code: def write_longlong(self, n, pack=Struct('>Q').pack):
          
          if 0 <= n <= 0xFFFFFFFFFFFFFFFF:
              self._output_buffer.extend(pack(n))
          else:
              raise ValueError(
                  'Longlong %d out of range 0..0xFFFFFFFFFFFFFFFF', n)
          return self
docs: Write an integer as an unsigned 64-bit value.