@rule('<STR_LIT>')<EOL><INDENT>def visit_first_filter(self, _, children):<DEDENT>
return children[<NUM_LIT:0>]<EOL>
The first filter, so not preceded by a dot, could be a slice (or number) or a filter.

        Arguments
        ---------
        _ (node) : parsimonious.nodes.Node.
        children : list
            - 0: a ``slice`` object or a ``Filter`` resource.

        Returns
        -------
        Filter or SliceFilter
            An instance of ``Filter`` if a filter, or ``SliceFilter`` if a number or a slice.

        Example
        -------

        >>> FiltersWithSlicingParserMixin('1', default_rule='FIRST_FILTER').data
        [1]
        >>> FiltersWithSlicingParserMixin('[1]', default_rule='FIRST_FILTER').data
        [1]
        >>> FiltersWithSlicingParserMixin('[1:2]', default_rule='FIRST_FILTER').data
        [1:2]
        >>> FiltersWithSlicingParserMixin('foo', default_rule='FIRST_FILTER').data
        .foo