@rule('<STR_LIT>')<EOL><INDENT>def visit_unnamed_args(self, _, children):<DEDENT>
return [children[<NUM_LIT:0>]] + (children[<NUM_LIT:1>] or [])<EOL>
Unnamed arguments of a filter.

        Arguments
        ---------
        _ (node) : parsimonious.nodes.Node.
        children : list
            - 0: instance of ``.resources.PosArg``, first unnamed argument
            - 1: list of instances of ``.resources.PosArg``, other unnamed arguments

        Returns
        -------
        list(.resources.NamedArg)
            List of  instances of ``.resources.PosArg``.

        Example
        -------

        >>> UnnamedArgsParserMixin(r'1', default_rule='UNNAMED_ARGS').data
        [1]
        >>> UnnamedArgsParserMixin(r'1, 2', default_rule='UNNAMED_ARGS').data
        [1, 2]
        >>> UnnamedArgsParserMixin(r'1,null, "foo"', default_rule='UNNAMED_ARGS').data
        [1, None, "foo"]