code: private boolean couldBeEnumCollection(int stackPos) {
          if (stack.getStackDepth() <= stackPos) {
              return false;
          }
  
          OpcodeStack.Item item = stack.getStackItem(stackPos);
  
          CollectionType userValue = (CollectionType) item.getUserValue();
          if (userValue != null) {
              return userValue == CollectionType.REGULAR;
          }
  
          String realClass = item.getSignature();
          return "Ljava/util/HashSet;".equals(realClass) || "Ljava/util/HashMap;".equals(realClass);
      }
docs: returns whether the item at the stackpos location isn't an enum collection but could be
  
  @param stackPos
  the position on the opstack to check
  
  @return whether the collection should be converted to an enum collection