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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 add_replacer(self, replacer):
 r"""Add all patterns from another replacer. All patterns and replacements from replacer are appended to the ones already defined. """

        self._pat = None
        self._pats.extend(replacer._pats)
        self._funs.extend(replacer._funs)