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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 to_op(self):
 """ Extracts the modification operation from the set. :rtype: dict, None """

        if not self._adds and not self._removes:
            return None
        changes = {}
        if self._adds:
            changes['adds'] = list(self._adds)
        if self._removes:
            changes['removes'] = list(self._removes)
        return changes