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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_internal_subnet(self, context_id, subnet_id):
 """Add an internal subnet to a tunnel context. :param int context_id: The id-value representing the context instance. :param int subnet_id: The id-value representing the internal subnet. :return bool: True if internal subnet addition was successful. """

        return self.context.addPrivateSubnetToNetworkTunnel(subnet_id,
                                                            id=context_id)