Check Drug.txt to ensure that we don't have small molecules in there

[gaurav]

Some would have gotten in as part of #335,

I think the general rule we want to implement is that drug formulations are biolink:Drug (e.g. "acetaminophen / aspirin / caffeine Oral Tablet [Arthriten Inflammatory Pain]"), but that the active ingredient should be considered a biolink:SmallMolecule or some other variety of biolink:ChemicalEntity.

It might also be useful to dig within ChemicalEntity.txt and look for things in there that should be properly categorized as a biolink:SmallMolecule.