<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def open_sensor( self, input_source: str, extra_cmd: Optional[str] = None ) -> Coroutine: """Open FFmpeg process a video stream for motion detection. Return a coroutine. """

        command = [
            "-an",
            "-filter:v",
            "select=gt(scene\\,{0})".format(self._changes / 100),
        ]

        # run ffmpeg, read output
        return self.start_worker(
            cmd=command,
            input_source=input_source,
            output="-f framemd5 -",
            extra_cmd=extra_cmd,
            pattern=self.MATCH,
            reading=FFMPEG_STDOUT,
        )