code: 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)
docs: Return a generic |_Marker| instance for the marker at *offset* in
          *stream* having *marker_code*.