@rule('<STR_LIT>')<EOL><INDENT>def visit_slice(self, _, children):<DEDENT>
return children[<NUM_LIT:1>]<EOL>
A slice or number contained in brackets (``[]``)

        Arguments
        ---------
        _ (node) : parsimonious.nodes.Node.
        children : list
            - 0: for ``BRA_O`` (opening bracket): ``None``.
            - 1: slice or number.
            - 2: for ``BRA_C`` (closing bracket): ``None``.

        Returns
        -------
        slice or number
            The slice or number got from ``children[1]``

        Example
        -------

        >>> SliceParserMixin('[1]', default_rule='SLICE').data
        1
        >>> SliceParserMixin('[:]', default_rule='SLICE').data
        slice(None, None, None)
        >>> SliceParserMixin('[1:]', default_rule='SLICE').data
        slice(1, None, None)
        >>> SliceParserMixin('[1:2:3]', default_rule='SLICE').data
        slice(1, 2, 3)