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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def is_restricted(self, assets, dt):
 """ Returns whether or not an asset or iterable of assets is restricted on a 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)
        )