Table1 returns non-unique entries

[Wojtekmi]

When using the FeatureExtraction package to prepare drug use tables I use a set of all ATC4 codes.
Due to the vocabulary having identical entry names for different codes (e.g. Ophthalmological and gynaecological antibiotics- S01AA and G01AArespectively - and are both called Antibiotics).
This makes them indistinguishable in the final table1, since it is uses concept_name as identifier.

This could be solved by optionally including concept_id as a unique identifier in table1.