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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 _map_in_out(self, inside_var_name):
 """Return the external name of a variable mapped from inside."""

        for out_name, in_name in self.outside_name_map.items():
            if inside_var_name == in_name:
                return out_name
        return None