docs: def get_pgpm_db_version(cls, cur, schema_name='_pgpm'):
          """
          returns current version of pgpm schema
          :return: tuple of major, minor and patch components of version
          """
          cls.set_search_path(cur, schema_name)
          cur.execute("SELECT _find_schema('{0}', '{1}')"
                      .format(schema_name, 'x'))
          # TODO: make it work with the way it's written below. currently throws error as func returns record
          # without column list
          # cur.callproc('_find_schema', [schema_name, 'x'])
          pgpm_v_ext = tuple(cur.fetchone()[0][1:-1].split(','))
  
          return pgpm_v_ext[2], pgpm_v_ext[3], pgpm_v_ext[4]