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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 _set_categories(self, categories, fastpath=False):
 """ Sets new categories inplace Parameters fastpath : bool, default False Don't perform validation of the categories for uniqueness or nulls Examples -------- [a, b] Categories (2, object):
 [a, b] [a, c] Categories (2, object):
 [a, c] """


        if fastpath:
            new_dtype = CategoricalDtype._from_fastpath(categories,
                                                        self.ordered)
        else:
            new_dtype = CategoricalDtype(categories, ordered=self.ordered)
        if (not fastpath and self.dtype.categories is not None and
                len(new_dtype.categories) != len(self.dtype.categories)):
            raise ValueError("new categories need to have the same number of "
                             "items than the old categories!")

        self._dtype = new_dtype