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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_categorical_astype(self, dtype):
 """ validate that we have a astypeable to categorical, returns a boolean if we are a categorical """

        if dtype is Categorical or dtype is CategoricalDtype:
            # this is a pd.Categorical, but is not
            # a valid type for astypeing
            raise TypeError("invalid type {0} for astype".format(dtype))

        elif is_categorical_dtype(dtype):
            return True

        return False