<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def run(self):
 """ For each incoming message, decode the JSON, evaluate expression, encode as JSON and write that to the output file. """

        for line in self.incoming:
            message = loads(line)
            result = self._evaluate(message)
            if result is self._SKIP:
                continue
            self.output.write(dumps(result, cls=_DatetimeJSONEncoder) + b"\n")