Add db_refs as list of strings and make pmids unique
Add db_refs as list of strings and make pmids unique

sorgerlab/belpy,johnbachman/belpy,johnbachman/belpy,bgyori/indra,johnbachman/belpy,bgyori/indra,johnbachman/indra,sorgerlab/belpy,sorgerlab/indra,johnbachman/indra,sorgerlab/belpy,sorgerlab/indra,bgyori/indra,johnbachman/indra,sorgerlab/indra