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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 _x_open(self):
 """Open a channel for use This method opens a virtual connection (a channel). RULE: This method MUST NOT be called when the channel is already open. PARAMETERS: out_of_band: shortstr (DEPRECATED) out-of-band settings Configures out-of-band transfers on this channel. The syntax and meaning of this field will be formally defined at a later date. """

        if self.is_open:
            return

        args = AMQPWriter()
        args.write_shortstr('')  # out_of_band: deprecated
        self._send_method((20, 10), args)
        return self.wait(allowed_methods=[
            (20, 11),  # Channel.open_ok
        ])