code: @Override
      public void _distinct() {
          if (isDistinct()) {
              throw new IllegalStateException("The is already a distinct query");
          }
  
          if (selectTokens.isEmpty()) {
              selectTokens.add(DistinctToken.INSTANCE);
          } else {
              selectTokens.add(0, DistinctToken.INSTANCE);
          }
      }
docs: TBD expr public string GetMemberQueryPath(Expression expression)