def subcommand_not_found(self, command, string):
        """|maybecoro|

        A method called when a command did not have a subcommand requested in the help command.
        This is useful to override for i18n.

        Defaults to either:

        - ``'Command "{command.qualified_name}" has no subcommands.'``
            - If there is no subcommand in the ``command`` parameter.
        - ``'Command "{command.qualified_name}" has no subcommand named {string}'``
            - If the ``command`` parameter has subcommands but not one named ``string``.

        Parameters
        ------------
        command: :class:`Command`
            The command that did not have the subcommand requested.
        string: :class:`str`
            The string that contains the invalid subcommand. Note that this has
            had mentions removed to prevent abuse.

        Returns
        ---------
        :class:`str`
            The string to use when the command did not have the subcommand requested.
        """
        if isinstance(command, Group) and len(command.all_commands) > 0:
            return 'Command "{0.qualified_name}" has no subcommand named {1}'.format(command, string)
        return 'Command "{0.qualified_name}" has no subcommands.'.format(command)