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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 _serialize(self):
 """ A helper method to build a dict of all mutable Properties of this object """

        result = { a: getattr(self, a) for a in type(self).properties
            if type(self).properties[a].mutable }

        for k, v in result.items():
            if isinstance(v, Base):
                result[k] = v.id

        return result