'Return a generic |_Marker| instance for the marker at *offset* in
*stream* having *marker_code*.'

@classmethod
def from_stream(cls, stream, marker_code, offset):

    if JPEG_MARKER_CODE.is_standalone(marker_code):
        segment_length = 0
    else:
        segment_length = stream.read_short(offset)
    return cls(marker_code, offset, segment_length)
