code: def write(self, fptr):
          
          fptr.write(struct.pack('>I4s',
                                 len(self.associations) * 4 + 8, b'nlst'))
  
          fmt = '>' + 'I' * len(self.associations)
          write_buffer = struct.pack(fmt, *self.associations)
          fptr.write(write_buffer)
docs: Write a NumberList box to file.