code: def _mask_to_bytes(self, mask):
          
          chunks = []
          shiftmask = (2 ** 64) - 1
          for x in range(16):
              chunks.append(struct.pack('<Q', mask & shiftmask))
              mask >>= 64
          return mitogen.core.b('').join(chunks)
docs: Convert the (type long) mask to a cpu_set_t.