@rule('<STR_LIT>')<EOL><INDENT>def visit_optional_args_content(self, _, children):<DEDENT>
return children[<NUM_LIT:0>] if children else []<EOL>
The optional arguments of a filter (part inside the parentheses).

        Arguments
        ---------
        _ (node) : parsimonious.nodes.Node.
        children : list
            - 1: list of instances of subclasses of ``.resources.Arg``.

        Returns
        -------
        list(.resources.Arg)
            List of  instances of subclasses of ``.resources.Arg``.

        Example
        -------

        >>> ArgsParserMixin(r'', default_rule='OPTIONAL_ARGS_CONTENT').data
        []
        >>> ArgsParserMixin(r'1', default_rule='OPTIONAL_ARGS_CONTENT').data
        [1]
        >>> ArgsParserMixin(r'foo="bar"', default_rule='OPTIONAL_ARGS_CONTENT').data
        [foo="bar"]
        >>> ArgsParserMixin(r'1, foo="bar"', default_rule='OPTIONAL_ARGS_CONTENT').data
        [1, foo="bar"]