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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 open_camera( self, input_source: str, extra_cmd: Optional[str] = None ) -> Coroutine: """Open FFmpeg process as mjpeg video stream. Return A coroutine. """

        command = ["-an", "-c:v", "mjpeg"]

        return self.open(
            cmd=command,
            input_source=input_source,
            output="-f mpjpeg -",
            extra_cmd=extra_cmd,
        )