added dm.test_dfs() for DFS availability

        try:

            tbl = gaia_query_from_dfs(

                ra=ra, dec=dec, radius=radius, min_mag=min_mag, max_mag=max_mag, obstime=obstime, limit=limit)

            assert len(tbl) > 0

            return tbl

        except Exception as e:

        except:

            print("Error occurred during the query!")

            return None

    def test_dfs(self):

        """ Test if DFS works. """

        try:

            tbl = gaia_query_from_dfs(radius=0.001)

            assert len(tbl) == 0

            return True

        except:

            return False

    def __repr__(self):

        lines = ""

        lines += "<CsstMsDataManager>\n"