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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 _release_command_buffer(self, command_buffer):
 """This is called by the command buffer when it closes."""

        if command_buffer.closed:
            return

        self._cb_poll.unregister(command_buffer.host_id)
        self.connection_pool.release(command_buffer.connection)
        command_buffer.connection = None