Pytest

http://classyfire.wishartlab.com/tax_nodes/C0000000
http://classyfire.wishartlab.com/tax_nodes/C0000264
http://classyfire.wishartlab.com/tax_nodes/C0000364
http://classyfire.wishartlab.com/tax_nodes/C0000517
http://classyfire.wishartlab.com/tax_nodes/C0000517
http://classyfire.wishartlab.com/tax_nodes/C0004557
http://classyfire.wishartlab.com/tax_nodes/C0000278
http://classyfire.wishartlab.com/tax_nodes/C0003940
http://classyfire.wishartlab.com/tax_nodes/C0004150
http://classyfire.wishartlab.com/tax_nodes/C0001831
https://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:48376
http://metacyc.org/META/new-image?type=COMPOUND&object=UREA
http://www.hmdb.ca/metabolites/HMDB0000294
http://www.genome.jp/dbget-bin/www_bget?drug:D00023
http://www.genome.jp/dbget-bin/www_bget?cpd:C00086
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=1176
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?sid=46508687
https://www.chemspider.com/Chemical-Structure.1143.html
http://www.bindingdb.org/bind/chemsearch/marvin/MolStructure.jsp?monomerid=24961
https://mor.nlm.nih.gov/RxNav/search?searchBy=RXCUI&searchTerm=11002
https://www.ebi.ac.uk/chebi/searchId.do?chebiId=16199
https://www.ebi.ac.uk/chembldb/index.php/compound/inspect/CHEMBL985
https://zinc.docking.org/substances/ZINC000008214514
http://www.pharmgkb.org/drug/PA451831
https://www.ebi.ac.uk/pdbe-srv/pdbechem/chemicalCompound/show/URE
https://www.drugs.com/cons/urea-intravenous.html
https://en.wikipedia.org/wiki/Urea