code: def get_proteins_psms_for_map(self):
          
          fields = ['p.gene_acc', 'sets.set_name',
                    'pep.sequence', 'psm.psm_id']
          firstjoin = ('protein_psm', 'pp', 'protein_acc')
          genetable = 'genes'
          return self.get_unique_gene_psms(genetable, fields, firstjoin)
docs: Gets gene-PSM combinations from DB and filters out uniques
          on the fly. Filtering is done since PSM are stored per protein,
          not per gene, so there may be a lot of *plicates