Return a list of hdf5 tables name PyMCsamples.

def _gettables(self):
        """Return a list of hdf5 tables name PyMCsamples.
        """

        groups = self._h5file.list_nodes("/")
        if len(groups) == 0:
            return []
        else:
            return [
                gr.PyMCsamples for gr in groups if gr._v_name[:5] == 'chain']