@dispatch(ClauseElement, Select)
def _join_selectables(a, b, condition=None, **kwargs):
    if len(b.froms) > 1:
        raise MDNotImplementedError()
    return b.replace_selectable(b.froms[0],
                                a.join(b.froms[0], condition, **kwargs))
dataset/ETHPy150Open blaze/blaze/blaze/compute/sql.py/_join_selectables/original