docs: def cat(self, numlines=None):
          """Return a list of lines output by this service."""
          if len(self.titles) == 1:
              lines = self.lines()
              if numlines is not None:
                  lines = lines[len(lines)-numlines:]
              log("\n".join(lines))
          else:
              lines = [self._printtuple(line[0], line[1]) for line in self.lines()]
              if numlines is not None:
                  lines = lines[len(lines)-numlines:]
              log("".join(lines))