def is_complex_subscript(self, leaf: Leaf) -> bool:
        """Return True iff `leaf` is part of a slice with non-trivial exprs."""
        open_lsqb = self.bracket_tracker.get_open_lsqb()
        if open_lsqb is None:
            return False

        subscript_start = open_lsqb.next_sibling

        if isinstance(subscript_start, Node):
            if subscript_start.type == syms.listmaker:
                return False

            if subscript_start.type == syms.subscriptlist:
                subscript_start = child_towards(subscript_start, leaf)

        return subscript_start is not None and any(
            n.type in TEST_DESCENDANTS for n in subscript_start.pre_order()
        )
Return True iff `leaf` is part of a slice with non-trivial exprs.
src/black/lines.py