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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 normalized(self, document, schema=None, always_return_document=False):
 """ Returns the document normalized according to the specified rules of a schema. :param document: The document to normalize. :type document: any :term:`mapping` :param schema: The validation schema. Defaults to :obj:`None`. If not provided here, the schema must have been provided at class instantiation. :type schema: any :term:`mapping` :param always_return_document: Return the document, even if an error occurred. Defaults to: ``False``. :type always_return_document: :class:`bool` :return: A normalized copy of the provided mapping or :obj:`None` if an error occurred during normalization. """

        self.__init_processing(document, schema)
        self.__normalize_mapping(self.document, self.schema)
        self.error_handler.end(self)
        if self._errors and not always_return_document:
            return None
        else:
            return self.document