diff --git a/Pipfile.lock b/Pipfile.lock
index abfefd3..2be7fe0 100644
--- a/Pipfile.lock
+++ b/Pipfile.lock
@@ -27,10 +27,10 @@
         },
         "certifi": {
             "hashes": [
-                "sha256:13e698f54293db9f89122b0581843a782ad0934a4fe0172d2a980ba77fc61bb7",
-                "sha256:9fa520c1bacfb634fa7af20a76bcbd3d5fb390481724c597da32c719a7dca4b0"
+                "sha256:1a4995114262bffbc2413b159f2a1a480c969de6e6eb13ee966d470af86af59c",
+                "sha256:719a74fb9e33b9bd44cc7f3a8d94bc35e4049deebe19ba7d8e108280cfd59830"
             ],
-            "version": "==2018.4.16"
+            "version": "==2020.12.5"
         },
         "chardet": {
             "hashes": [
@@ -55,38 +55,49 @@
         },
         "lxml": {
             "hashes": [
-                "sha256:0941f4313208c07734410414d8308812b044fd3fb98573454e3d3a0d2e201f3d",
-                "sha256:0b18890aa5730f9d847bc5469e8820f782d72af9985a15a7552109a86b01c113",
-                "sha256:21f427945f612ac75576632b1bb8c21233393c961f2da890d7be3927a4b6085f",
-                "sha256:24cf6f622a4d49851afcf63ac4f0f3419754d4e98a7a548ab48dd03c635d9bd3",
-                "sha256:2dc6705486b8abee1af9e2a3761e30a3cb19e8276f20ca7e137ee6611b93707c",
-                "sha256:2e43b2e5b7d2b9abe6e0301eef2c2c122ab45152b968910eae68bdee2c4cfae0",
-                "sha256:329a6d8b6d36f7d6f8b6c6a1db3b2c40f7e30a19d3caf62023c9d6a677c1b5e1",
-                "sha256:423cde55430a348bda6f1021faad7235c2a95a6bdb749e34824e5758f755817a",
-                "sha256:4651ea05939374cfb5fe87aab5271ed38c31ea47997e17ec3834b75b94bd9f15",
-                "sha256:4be3bbfb2968d7da6e5c2cd4104fc5ec1caf9c0794f6cae724da5a53b4d9f5a3",
-                "sha256:622f7e40faef13d232fb52003661f2764ce6cdef3edb0a59af7c1559e4cc36d1",
-                "sha256:664dfd4384d886b239ef0d7ee5cff2b463831079d250528b10e394a322f141f9",
-                "sha256:697c0f58ac637b11991a1bc92e07c34da4a72e2eda34d317d2c1c47e2f24c1b3",
-                "sha256:6ec908b4c8a4faa7fe1a0080768e2ce733f268b287dfefb723273fb34141475f",
-                "sha256:7ec3fe795582b75bb49bb1685ffc462dbe38d74312dac07ce386671a28b5316b",
-                "sha256:8c39babd923c431dcf1e5874c0f778d3a5c745a62c3a9b6bd755efd489ee8a1d",
-                "sha256:949ca5bc56d6cb73d956f4862ba06ad3c5d2808eac76304284f53ae0c8b2334a",
-                "sha256:9f0daddeefb0791a600e6195441910bdf01eac470be596b9467e6122b51239a6",
-                "sha256:a359893b01c30e949eae0e8a85671a593364c9f0b8162afe0cb97317af0953bf",
-                "sha256:ad5d5d8efed59e6b1d4c50c1eac59fb6ecec91b2073676af1e15fc4d43e9b6c5",
-                "sha256:bc1a36f95a6b3667c09b34995fc3a46a82e4cf0dc3e7ab281e4c77b15bd7af05",
-                "sha256:be37b3f55b6d7d923f43bf74c356fc1878eb36e28505f38e198cb432c19c7b1a",
-                "sha256:c45bca5e544eb75f7500ffd730df72922eb878a2f0213b0dc5a5f357ded3a85d",
-                "sha256:ccee7ebbb4735ebc341d347fca9ee09f2fa6c0580528c1414bc4e1d31372835c",
-                "sha256:dc62c0840b2fc7753550b40405532a3e125c0d3761f34af948873393aa688160",
-                "sha256:f7d9d5aa1c7e54167f1a3cba36b5c52c7c540f30952c9bd7d9302a1eda318424"
+                "sha256:079f3ae844f38982d156efce585bc540c16a926d4436712cf4baee0cce487a3d",
+                "sha256:0fbcf5565ac01dff87cbfc0ff323515c823081c5777a9fc7703ff58388c258c3",
+                "sha256:122fba10466c7bd4178b07dba427aa516286b846b2cbd6f6169141917283aae2",
+                "sha256:1b7584d421d254ab86d4f0b13ec662a9014397678a7c4265a02a6d7c2b18a75f",
+                "sha256:26e761ab5b07adf5f555ee82fb4bfc35bf93750499c6c7614bd64d12aaa67927",
+                "sha256:289e9ca1a9287f08daaf796d96e06cb2bc2958891d7911ac7cae1c5f9e1e0ee3",
+                "sha256:2a9d50e69aac3ebee695424f7dbd7b8c6d6eb7de2a2eb6b0f6c7db6aa41e02b7",
+                "sha256:33bb934a044cf32157c12bfcfbb6649807da20aa92c062ef51903415c704704f",
+                "sha256:3439c71103ef0e904ea0a1901611863e51f50b5cd5e8654a151740fde5e1cade",
+                "sha256:39b78571b3b30645ac77b95f7c69d1bffc4cf8c3b157c435a34da72e78c82468",
+                "sha256:4289728b5e2000a4ad4ab8da6e1db2e093c63c08bdc0414799ee776a3f78da4b",
+                "sha256:4bff24dfeea62f2e56f5bab929b4428ae6caba2d1eea0c2d6eb618e30a71e6d4",
+                "sha256:542d454665a3e277f76954418124d67516c5f88e51a900365ed54a9806122b83",
+                "sha256:5a0a14e264069c03e46f926be0d8919f4105c1623d620e7ec0e612a2e9bf1c04",
+                "sha256:66e575c62792c3f9ca47cb8b6fab9e35bab91360c783d1606f758761810c9791",
+                "sha256:74f7d8d439b18fa4c385f3f5dfd11144bb87c1da034a466c5b5577d23a1d9b51",
+                "sha256:7610b8c31688f0b1be0ef882889817939490a36d0ee880ea562a4e1399c447a1",
+                "sha256:76fa7b1362d19f8fbd3e75fe2fb7c79359b0af8747e6f7141c338f0bee2f871a",
+                "sha256:7728e05c35412ba36d3e9795ae8995e3c86958179c9770e65558ec3fdfd3724f",
+                "sha256:8157dadbb09a34a6bd95a50690595e1fa0af1a99445e2744110e3dca7831c4ee",
+                "sha256:820628b7b3135403540202e60551e741f9b6d3304371712521be939470b454ec",
+                "sha256:884ab9b29feaca361f7f88d811b1eea9bfca36cf3da27768d28ad45c3ee6f969",
+                "sha256:89b8b22a5ff72d89d48d0e62abb14340d9e99fd637d046c27b8b257a01ffbe28",
+                "sha256:92e821e43ad382332eade6812e298dc9701c75fe289f2a2d39c7960b43d1e92a",
+                "sha256:b007cbb845b28db4fb8b6a5cdcbf65bacb16a8bd328b53cbc0698688a68e1caa",
+                "sha256:bc4313cbeb0e7a416a488d72f9680fffffc645f8a838bd2193809881c67dd106",
+                "sha256:bccbfc27563652de7dc9bdc595cb25e90b59c5f8e23e806ed0fd623755b6565d",
+                "sha256:c4f05c5a7c49d2fb70223d0d5bcfbe474cf928310ac9fa6a7c6dddc831d0b1d4",
+                "sha256:ce256aaa50f6cc9a649c51be3cd4ff142d67295bfc4f490c9134d0f9f6d58ef0",
+                "sha256:d2e35d7bf1c1ac8c538f88d26b396e73dd81440d59c1ef8522e1ea77b345ede4",
+                "sha256:df7c53783a46febb0e70f6b05df2ba104610f2fb0d27023409734a3ecbb78fb2",
+                "sha256:efac139c3f0bf4f0939f9375af4b02c5ad83a622de52d6dfa8e438e8e01d0eb0",
+                "sha256:efd7a09678fd8b53117f6bae4fa3825e0a22b03ef0a932e070c0bdbb3a35e654",
+                "sha256:f2380a6376dfa090227b663f9678150ef27543483055cc327555fb592c5967e2",
+                "sha256:f8380c03e45cf09f8557bdaa41e1fa7c81f3ae22828e1db470ab2a6c96d8bc23",
+                "sha256:f90ba11136bfdd25cae3951af8da2e95121c9b9b93727b1b896e3fa105b2f586"
             ],
             "index": "pypi",
-            "version": "==4.2.3"
+            "version": "==4.6.3"
         },
         "rdflib": {
-            "git": "https://github.com/RDFLib/rdflib.git"
+            "git": "https://github.com/RDFLib/rdflib.git",
+            "ref": "d717cef505b07556fffc9f0e64d6c8f5b3a5b84c"
         },
         "requests": {
             "hashes": [
@@ -115,34 +126,35 @@
     "develop": {
         "atomicwrites": {
             "hashes": [
-                "sha256:240831ea22da9ab882b551b31d4225591e5e447a68c5e188db5b89ca1d487585",
-                "sha256:a24da68318b08ac9c9c45029f4a10371ab5b20e4226738e150e6e7c571630ae6"
+                "sha256:6d1784dea7c0c8d4a5172b6c620f40b6e4cbfdf96d783691f2e1302a7b88e197",
+                "sha256:ae70396ad1a434f9c7046fd2dd196fc04b12f9e91ffb859164193be8b6168a7a"
             ],
-            "version": "==1.1.5"
+            "version": "==1.4.0"
         },
         "attrs": {
             "hashes": [
-                "sha256:4b90b09eeeb9b88c35bc642cbac057e45a5fd85367b985bd2809c62b7b939265",
-                "sha256:e0d0eb91441a3b53dab4d9b743eafc1ac44476296a2053b6ca3af0b139faf87b"
+                "sha256:31b2eced602aa8423c2aea9c76a724617ed67cf9513173fd3a4f03e3a929c7e6",
+                "sha256:832aa3cde19744e49938b91fea06d69ecb9e649c93ba974535d08ad92164f700"
             ],
-            "version": "==18.1.0"
+            "version": "==20.3.0"
         },
         "backcall": {
             "hashes": [
-                "sha256:38ecd85be2c1e78f77fd91700c76e14667dc21e2713b63876c0eb901196e01e4",
-                "sha256:bbbf4b1e5cd2bdb08f915895b51081c041bac22394fdfcfdfbe9f14b77c08bf2"
+                "sha256:5cbdbf27be5e7cfadb448baf0aa95508f91f2bbc6c6437cd9cd06e2a4c215e1e",
+                "sha256:fbbce6a29f263178a1f7915c1940bde0ec2b2a967566fe1c65c1dfb7422bd255"
             ],
-            "version": "==0.1.0"
+            "version": "==0.2.0"
         },
         "coverage": {
             "hashes": [
                 "sha256:03481e81d558d30d230bc12999e3edffe392d244349a90f4ef9b88425fac74ba",
                 "sha256:0b136648de27201056c1869a6c0d4e23f464750fd9a9ba9750b8336a244429ed",
-                "sha256:104ab3934abaf5be871a583541e8829d6c19ce7bde2923b2751e0d3ca44db60a",
-                "sha256:15b111b6a0f46ee1a485414a52a7ad1d703bdf984e9ed3c288a4414d3871dcbd",
+                "sha256:0bf8cbbd71adfff0ef1f3a1531e6402d13b7b01ac50a79c97ca15f030dba6306",
+                "sha256:10a46017fef60e16694a30627319f38a2b9b52e90182dddb6e37dcdab0f4bf95",
                 "sha256:198626739a79b09fa0a2f06e083ffd12eb55449b5f8bfdbeed1df4910b2ca640",
-                "sha256:1c383d2ef13ade2acc636556fd544dba6e14fa30755f26812f54300e401f98f2",
+                "sha256:23d341cdd4a0371820eb2b0bd6b88f5003a7438bbedb33688cd33b8eae59affd",
                 "sha256:28b2191e7283f4f3568962e373b47ef7f0392993bb6660d079c62bd50fe9d162",
+                "sha256:2a5b73210bad5279ddb558d9a2bfedc7f4bf6ad7f3c988641d83c40293deaec1",
                 "sha256:2eb564bbf7816a9d68dd3369a510be3327f1c618d2357fa6b1216994c2e3d508",
                 "sha256:337ded681dd2ef9ca04ef5d93cfc87e52e09db2594c296b4a0a3662cb1b41249",
                 "sha256:3a2184c6d797a125dca8367878d3b9a178b6fdd05fdc2d35d758c3006a1cd694",
@@ -162,26 +174,22 @@
                 "sha256:7e1fe19bd6dce69d9fd159d8e4a80a8f52101380d5d3a4d374b6d3eae0e5de9c",
                 "sha256:8c3cb8c35ec4d9506979b4cf90ee9918bc2e49f84189d9bf5c36c0c1119c6558",
                 "sha256:9d6dd10d49e01571bf6e147d3b505141ffc093a06756c60b053a859cb2128b1f",
-                "sha256:9e112fcbe0148a6fa4f0a02e8d58e94470fc6cb82a5481618fea901699bf34c4",
-                "sha256:ac4fef68da01116a5c117eba4dd46f2e06847a497de5ed1d64bb99a5fda1ef91",
-                "sha256:b8815995e050764c8610dbc82641807d196927c3dbed207f0a079833ffcf588d",
                 "sha256:be6cfcd8053d13f5f5eeb284aa8a814220c3da1b0078fa859011c7fffd86dab9",
                 "sha256:c1bb572fab8208c400adaf06a8133ac0712179a334c09224fb11393e920abcdd",
                 "sha256:de4418dadaa1c01d497e539210cb6baa015965526ff5afc078c57ca69160108d",
                 "sha256:e05cb4d9aad6233d67e0541caa7e511fa4047ed7750ec2510d466e806e0255d6",
-                "sha256:e4d96c07229f58cb686120f168276e434660e4358cc9cf3b0464210b04913e77",
-                "sha256:f3f501f345f24383c0000395b26b726e46758b71393267aeae0bd36f8b3ade80",
-                "sha256:f8a923a85cb099422ad5a2e345fe877bbc89a8a8b23235824a93488150e45f6e"
+                "sha256:f05a636b4564104120111800021a92e43397bc12a5c72fed7036be8556e0029e",
+                "sha256:f3f501f345f24383c0000395b26b726e46758b71393267aeae0bd36f8b3ade80"
             ],
             "index": "pypi",
             "version": "==4.5.1"
         },
         "decorator": {
             "hashes": [
-                "sha256:2c51dff8ef3c447388fe5e4453d24a2bf128d3a4c32af3fabef1f01c6851ab82",
-                "sha256:c39efa13fbdeb4506c476c9b3babf6a718da943dab7811c206005a4a956c080c"
+                "sha256:41fa54c2a0cc4ba648be4fd43cff00aedf5b9465c9bf18d64325bc225f08f760",
+                "sha256:e3a62f0520172440ca0dcc823749319382e377f37f140a0b99ef45fecb84bfe7"
             ],
-            "version": "==4.3.0"
+            "version": "==4.4.2"
         },
         "flake8": {
             "hashes": [
@@ -208,10 +216,10 @@
         },
         "jedi": {
             "hashes": [
-                "sha256:b409ed0f6913a701ed474a614a3bb46e6953639033e31f769ca7581da5bd1ec1",
-                "sha256:c254b135fb39ad76e78d4d8f92765ebc9bf92cbc76f49e97ade1d5f5121e1f6f"
+                "sha256:18456d83f65f400ab0c2d3319e48520420ef43b23a086fdc05dff34132f0fb93",
+                "sha256:92550a404bad8afed881a137ec9a461fed49eca661414be45059329614ed0707"
             ],
-            "version": "==0.12.1"
+            "version": "==0.18.0"
         },
         "mccabe": {
             "hashes": [
@@ -222,33 +230,32 @@
         },
         "more-itertools": {
             "hashes": [
-                "sha256:2b6b9893337bfd9166bee6a62c2b0c9fe7735dcf85948b387ec8cba30e85d8e8",
-                "sha256:6703844a52d3588f951883005efcf555e49566a48afd4db4e965d69b883980d3",
-                "sha256:a18d870ef2ffca2b8463c0070ad17b5978056f403fb64e3f15fe62a52db21cc0"
+                "sha256:5652a9ac72209ed7df8d9c15daf4e1aa0e3d2ccd3c87f8265a0673cd9cbc9ced",
+                "sha256:c5d6da9ca3ff65220c3bfd2a8db06d698f05d4d2b9be57e1deb2be5a45019713"
             ],
-            "version": "==4.2.0"
+            "version": "==8.7.0"
         },
         "parso": {
             "hashes": [
-                "sha256:35704a43a3c113cce4de228ddb39aab374b8004f4f2407d070b6a2ca784ce8a2",
-                "sha256:895c63e93b94ac1e1690f5fdd40b65f07c8171e3e53cbd7793b5b96c0e0a7f24"
+                "sha256:12b83492c6239ce32ff5eed6d3639d6a536170723c6f3f1506869f1ace413398",
+                "sha256:a8c4922db71e4fdb90e0d0bc6e50f9b273d3397925e5e60a717e719201778d22"
             ],
-            "version": "==0.3.1"
+            "version": "==0.8.2"
         },
         "pexpect": {
             "hashes": [
-                "sha256:2a8e88259839571d1251d278476f3eec5db26deb73a70be5ed5dc5435e418aba",
-                "sha256:3fbd41d4caf27fa4a377bfd16fef87271099463e6fa73e92a52f92dfee5d425b"
+                "sha256:0b48a55dcb3c05f3329815901ea4fc1537514d6ba867a152b581d69ae3710937",
+                "sha256:fc65a43959d153d0114afe13997d439c22823a27cefceb5ff35c2178c6784c0c"
             ],
             "markers": "sys_platform != 'win32'",
-            "version": "==4.6.0"
+            "version": "==4.8.0"
         },
         "pickleshare": {
             "hashes": [
-                "sha256:84a9257227dfdd6fe1b4be1319096c20eb85ff1e82c7932f36efccfe1b09737b",
-                "sha256:c9a2541f25aeabc070f12f452e1f2a8eae2abd51e1cd19e8430402bdf4c1d8b5"
+                "sha256:87683d47965c1da65cdacaf31c8441d12b8044cdec9aca500cd78fc2c683afca",
+                "sha256:9649af414d74d4df115d5d718f82acb59c9d418196b7b4290ed47a12ce62df56"
             ],
-            "version": "==0.7.4"
+            "version": "==0.7.5"
         },
         "pluggy": {
             "hashes": [
@@ -260,25 +267,25 @@
         },
         "prompt-toolkit": {
             "hashes": [
-                "sha256:1df952620eccb399c53ebb359cc7d9a8d3a9538cb34c5a1344bdbeb29fbcc381",
-                "sha256:3f473ae040ddaa52b52f97f6b4a493cfa9f5920c255a12dc56a7d34397a398a4",
-                "sha256:858588f1983ca497f1cf4ffde01d978a3ea02b01c8a26a8bbc5cd2e66d816917"
+                "sha256:37925b37a4af1f6448c76b7606e0285f79f434ad246dda007a27411cca730c6d",
+                "sha256:dd4fca02c8069497ad931a2d09914c6b0d1b50151ce876bc15bde4c747090126",
+                "sha256:f7eec66105baf40eda9ab026cd8b2e251337eea8d111196695d82e0c5f0af852"
             ],
-            "version": "==1.0.15"
+            "version": "==1.0.18"
         },
         "ptyprocess": {
             "hashes": [
-                "sha256:923f299cc5ad920c68f2bc0bc98b75b9f838b93b599941a6b63ddbc2476394c0",
-                "sha256:d7cc528d76e76342423ca640335bd3633420dc1366f258cb31d05e865ef5ca1f"
+                "sha256:4b41f3967fce3af57cc7e94b888626c18bf37a083e3651ca8feeb66d492fef35",
+                "sha256:5c5d0a3b48ceee0b48485e0c26037c0acd7d29765ca3fbb5cb3831d347423220"
             ],
-            "version": "==0.6.0"
+            "version": "==0.7.0"
         },
         "py": {
             "hashes": [
-                "sha256:3fd59af7435864e1a243790d322d763925431213b6b8529c6ca71081ace3bbf7",
-                "sha256:e31fb2767eb657cbde86c454f02e99cb846d3cd9d61b318525140214fdc0e98e"
+                "sha256:21b81bda15b66ef5e1a777a21c4dcd9c20ad3efd0b3f817e7a809035269e1bd3",
+                "sha256:3b80836aa6d1feeaa108e046da6423ab8f6ceda6468545ae8d02d9d58d18818a"
             ],
-            "version": "==1.5.4"
+            "version": "==1.10.0"
         },
         "pycodestyle": {
             "hashes": [
@@ -296,10 +303,10 @@
         },
         "pygments": {
             "hashes": [
-                "sha256:78f3f434bcc5d6ee09020f92ba487f95ba50f1e3ef83ae96b9d5ffa1bab25c5d",
-                "sha256:dbae1046def0efb574852fab9e90209b23f556367b5a320c0bcb871c77c3e8cc"
+                "sha256:2656e1a6edcdabf4275f9a3640db59fd5de107d88e8663c5d4e9a0fa62f77f94",
+                "sha256:534ef71d539ae97d4c3a4cf7d6f110f214b0e687e92f9cb9d2a3b0d3101289c8"
             ],
-            "version": "==2.2.0"
+            "version": "==2.8.1"
         },
         "pytest": {
             "hashes": [
@@ -317,24 +324,24 @@
         },
         "six": {
             "hashes": [
-                "sha256:70e8a77beed4562e7f14fe23a786b54f6296e34344c23bc42f07b15018ff98e9",
-                "sha256:832dc0e10feb1aa2c68dcc57dbb658f1c7e65b9b61af69048abc87a2db00a0eb"
+                "sha256:30639c035cdb23534cd4aa2dd52c3bf48f06e5f4a941509c8bafd8ce11080259",
+                "sha256:8b74bedcbbbaca38ff6d7491d76f2b06b3592611af620f8426e82dddb04a5ced"
             ],
-            "version": "==1.11.0"
+            "version": "==1.15.0"
         },
         "traitlets": {
             "hashes": [
-                "sha256:9c4bd2d267b7153df9152698efb1050a5d84982d3384a37b2c1f7723ba3e7835",
-                "sha256:c6cb5e6f57c5a9bdaa40fa71ce7b4af30298fbab9ece9815b5d995ab6217c7d9"
+                "sha256:70b4c6a1d9019d7b4f6846832288f86998aa3b9207c6821f3578a6a6a467fe44",
+                "sha256:d023ee369ddd2763310e4c3eae1ff649689440d4ae59d7485eb4cfbbe3e359f7"
             ],
-            "version": "==4.3.2"
+            "version": "==4.3.3"
         },
         "wcwidth": {
             "hashes": [
-                "sha256:3df37372226d6e63e1b1e1eda15c594bca98a22d33a23832a90998faa96bc65e",
-                "sha256:f4ebe71925af7b40a864553f761ed559b43544f8f71746c2d756c7fe788ade7c"
+                "sha256:beb4802a9cebb9144e99086eff703a642a13d6a0052920003a230f3294bbe784",
+                "sha256:c4d647b99872929fdb7bdcaa4fbe7f01413ed3d98077df798530e5b04f116c83"
             ],
-            "version": "==0.1.7"
+            "version": "==0.2.5"
         }
     }
 }