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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 _post_clean(self):
 """ Rewrite the error dictionary, so that its keys correspond to the model fields. """

        super(NgModelFormMixin, self)._post_clean()
        if self._errors and self.prefix:
            self._errors = ErrorDict((self.add_prefix(name), value) for name, value in self._errors.items())