remove implication son_swap (125) -> child_swap (161)
remove implication daughter_swap (27) -> child_swap (161)
remove implication child_swap (161) -> relative_swap (248)
remove implication brother_swap (63) -> sibling_swap (78)
remove implication sister_swap (67) -> sibling_swap (78)
remove implication sibling_swap (78) -> relative_swap (248)