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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 mjpeg_url(self, channelno=None, typeno=None):
 """ Return MJPEG streaming url Params: channelno: integer, the video channel index which starts from 1, default 1 if not specified. typeno: the stream type, default 0 if not specified. It can be the following value: 0-Main Stream 1-Extra Stream 1 (Sub Stream) 2-Extra Stream 2 (Sub Stream) """

        if channelno is None:
            channelno = 0

        if typeno is None:
            typeno = 1

        cmd = "mjpg/video.cgi?channel={0}&subtype={1}".format(
            channelno, typeno)
        return '{0}{1}'.format(self._base_url, cmd)