code: def find_missing_projections(label_list, projections):
      unmapped_combinations = set()
      if WILDCARD_COMBINATION in projections:
          return []
      for labeled_segment in label_list.ranges():
          combination = tuple(sorted([label.value for label in labeled_segment[2]]))
          if combination not in projections:
              unmapped_combinations.add(combination)
      return sorted(unmapped_combinations)