def _create_pipe(self):
        """
        Creates a new pipe and returns the child end of the connection.
        To request an account from the pipe, use::

            pipe = queue._create_pipe()

            # Let the account manager choose an account.
            pipe.send(('acquire-account-for-host', host))
            account = pipe.recv()
            ...
            pipe.send(('release-account', account.id()))

            # Or acquire a specific account.
            pipe.send(('acquire-account', account.id()))
            account = pipe.recv()
            ...
            pipe.send(('release-account', account.id()))

            pipe.close()
        """
        child = _PipeHandler(self.account_manager)
        self.pipe_handlers[id(child)] = child
        child.start()
        return child.to_parent
Creates a new pipe and returns the child end of the connection.
        To request an account from the pipe, use::

            pipe = queue._create_pipe()

            # Let the account manager choose an account.
            pipe.send(('acquire-account-for-host', host))
            account = pipe.recv()
            ...
            pipe.send(('release-account', account.id()))

            # Or acquire a specific account.
            pipe.send(('acquire-account', account.id()))
            account = pipe.recv()
            ...
            pipe.send(('release-account', account.id()))

            pipe.close()