code: @Override
      public ValueComparator compare(Value val) {
          if (val == null || val.getType() != ValueType.VALUELIST) {
              return ValueComparator.NOT_EQUAL_TO;
          }
          ValueList<?> vl = (ValueList<?>) val;
          return vl.contains(this) ? ValueComparator.IN : ValueComparator.NOT_IN;
      }
docs: Compares a value list for membership in another value list. This method
  does <b>NOT</b> compare two lists for equality. To do this, use
  {@link #equals(java.lang.Object) }.
  
  @param o a {@link Value}.
  @return if the provided value is a value list, returns
  {@link ValueComparator#IN} if the list is in the provided value list, or
  {@link ValueComparator#NOT_IN} if not. If the provided value is
  not a list, returns {@Link ValueComparator#UNKNOWN}.