docs: def output(self, kind, line):
          "*line* should be bytes"
          self.destination.write(b''.join([
              self._cyan,
              b't=%07d' % (time.time() - self._t0),
              self._reset,
              self._kind_prefixes[kind],
              self.markers[kind],
              line,
              self._reset,
          ]))
          self.destination.flush()