code: def get_proteins_for_peptide(self, psm_id):
          
          protsql = self.get_sql_select(['protein_acc'], 'protein_psm')
          protsql = '{0} WHERE psm_id=?'.format(protsql)
          cursor = self.get_cursor()
          proteins = cursor.execute(protsql, psm_id).fetchall()
          return [x[0] for x in proteins]
docs: Returns list of proteins for a passed psm_id