code: def parse_command_line(self, argv=None):
          
          conflicting_flags = set(['--user', '--system', '--sys-prefix'])
  
          if len(conflicting_flags.intersection(set(argv))) > 1:
              raise serverextensions.ArgumentConflict(
                  'cannot specify more than one of user, sys_prefix, or system')
          return super(ToggleJupyterTensorboardApp,
                       self).parse_command_line(argv)
docs: Overriden to check for conflicting flags
          Since notebook version doesn't do it well (or, indeed, at all)