code: def _parse_rgn_segment(cls, fptr):
          
          offset = fptr.tell() - 2
  
          read_buffer = fptr.read(2)
          length, = struct.unpack('>H', read_buffer)
  
          nbytes = 3 if cls._csiz < 257 else 4
          fmt = '>BBB' if cls._csiz < 257 else '>HBB'
          read_buffer = fptr.read(nbytes)
          data = struct.unpack(fmt, read_buffer)
  
          length = length
          crgn = data[0]
          srgn = data[1]
          sprgn = data[2]
  
          return RGNsegment(crgn, srgn, sprgn, length, offset)
docs: Parse the RGN segment.
  
          Parameters
          ----------
          fptr : file
              Open file object.
  
          Returns
          -------
          RGNSegment
              The current RGN segment.