def _validate(ds, params):
    if isinstance(ds, T.DataShape):
        # Check ellipses
        ellipses = [x for x in ds.parameters if isinstance(x, T.Ellipsis)]
        if len(ellipses) > 1:
            raise TypeError("Can only use a single wildcard")
        elif isinstance(ds.parameters[-1], T.Ellipsis):
            raise TypeError("Measure may not be an Ellipsis (...)")
dataset/ETHPy150Open blaze/datashape/datashape/validation.py/_validate/original