code: def do_help(self, arg):
          
          if not arg:
              return cmd.Cmd.do_help(self, arg)
          try:
              try:
                  topic = getattr(self, 'help_' + arg)
                  return topic()
              except AttributeError:
                  command = getattr(self, 'do_' + arg)
          except AttributeError:
              self.error('No help for %r' % arg)
          else:
              if sys.flags.optimize >= 2:
                  self.error('No help for %r; please do not run Python with -OO '
                             'if you need command help' % arg)
                  return
              self.message(command.__doc__.rstrip())
docs: h(elp)
          Without argument, print the list of available commands.
          With a command name as argument, print help about that command.
          "help pdb" shows the full pdb documentation.
          "help exec" gives help on the ! command.