@classmethod
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'))
    pgpm_v_ext = tuple(cur.fetchone()[0][1:-1].split(','))
    return pgpm_v_ext[2], pgpm_v_ext[3], pgpm_v_ext[4]
