update styler to only modify LineString

lib/cartopy/mpl/geoaxes.py

@@ -752,21 +752,19 @@ def add_geometries(self, geoms, crs, **kwargs):
 
 
         """
-        styler = kwargs.pop('styler', None)
-        has_LineString = False
-        try:
-            for g in iter(tuple(geoms)):
-                if isinstance(g, sgeom.LineString):
-                    has_LineString = True
-                    break
-        except TypeError:
-            if isinstance(geoms, sgeom.LineString):
-                has_LineString = True
-
-        if has_LineString:
-            kwargs['facecolor'] = 'none'
-            if 'edgecolor' not in kwargs or kwargs['edgecolor'] == 'face':
-                kwargs['edgecolor'] = mpl.rcParams['patch.edgecolor']
+        styler_kw = kwargs.pop('styler', None)
+
+        def styler(geom):
+            styler_g = styler_kw if styler_kw else dict()
+            styler_g = styler_g.copy()
+
+            if isinstance(geom, sgeom.LineString):
+                styler_g['facecolor'] = 'none'
+                if ('edgecolor' not in styler_g) or (styler_g['edgecolor'] ==
+                                                     'face'):
+                    styler_g['edgecolor'] = mpl.rcParams['patch.edgecolor']
+            return styler_g
+
         feature = cartopy.feature.ShapelyFeature(geoms, crs, **kwargs)
         return self.add_feature(feature, styler=styler)