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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 write_switch(self, module_address, state, callback_fn):

 """Set relay state."""

        _LOGGER.info("write_switch: setstate,{},{}{}"
                     .format(module_address, str(state), chr(13)))
        self.subscribe("state," + module_address, callback_fn)
        self.send("setstate,{},{}{}"
                  .format(module_address, str(state), chr(13)))