'Returns whether or not an asset or iterable of assets is restricted
on a dt.'

def is_restricted(self, assets, dt):

    if isinstance(assets, Asset):
        return self._is_restricted_for_asset(assets, dt)
    is_restricted = partial(self._is_restricted_for_asset, dt=dt)
    return pd.Series(index=pd.Index(assets), data=vectorize(is_restricted, otypes=[bool])(assets))
