pass 0: "level_1" exactly matches "level_1"
pass 1: "level_1 level_2" exactly matches "level_1 level_2"
pass 2: "level_1 level_2 level_3" exactly matches "level_1 level_2 level_3"
pass 3: "level_1" contained in "level_1 level_2 level_3"
pass 3: "level_1" contained in "level_1 level_2"
pass 3: "level_1" contained in "level_1"
pass 4: "level_1 level_2" contained in "level_1 level_2 level_3"
pass 4: "level_1 level_2" contained in "level_1 level_2"
pass 5: "level_1 level_2 level_3" contained in "level_1 level_2 level_3"
pass 6: "" exactly matches ""
pass 7: "" contained in ""