Returns the address of the closer of the channel.

def closing_address(self, block_identifier: BlockSpecification) -> Optional[Address]:
        """ Returns the address of the closer of the channel. """
        return self.token_network.closing_address(
            participant1=self.participant1,
            participant2=self.participant2,
            block_identifier=block_identifier,
            channel_identifier=self.channel_identifier,
        )