Handles showing help information for arguments provided.

            `env`
                Runtime ``Environment`` instance.
            `args`
                List of argument strings passed.

            Returns ``False`` if nothing handled.

            * Raises ``HelpBanner`` exception if valid subcommand provided.

def _handle_help(self, env, args):
        """ Handles showing help information for arguments provided.

            `env`
                Runtime ``Environment`` instance.
            `args`
                List of argument strings passed.

            Returns ``False`` if nothing handled.

            * Raises ``HelpBanner`` exception if valid subcommand provided.
            """

        if args:
            # command help (focus help [command])
            # get command plugin registered for command
            active = env.task.active
            plugin_obj = registration.get_command_hook(args[0], active)

            if plugin_obj:
                parser = self._get_plugin_parser(plugin_obj)
                raise HelpBanner(parser.format_help(), code=0)

        return False