feat: add function that returns cif filenames based on chemical formula

[yucongalicechen]

Task 2 in #331
@sbillinge ready for review

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (a51b553) to head (4c1521f).

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #336   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            9         9           
  Lines          516       525    +9     
=========================================
+ Hits           516       525    +9     

Files with missing lines	Coverage Δ
tests/test_tools.py	100.00% <100.00%> (ø)

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[sbillinge]

is there a reason you are using beautiful soup and not making an API call to COD?

[yucongalicechen]

is there a reason you are using beautiful soup and not making an API call to COD?

Whoops not really, that was a mistake. I've corrected the function now :)

[sbillinge]

that looks better. What is the payload from the API call? I am a bit confused that there are cif files involved. Doesn't it send json or sthg like that?