code: public static ImmutableList<Expression<?>> distinctList(Expression<?>... args) {
          final ImmutableList.Builder<Expression<?>> builder = ImmutableList.builder();
          final Set<Expression<?>> set = new HashSet<Expression<?>>(args.length);
          for (Expression<?> arg : args) {
              if (set.add(arg)) {
                  builder.add(arg);
              }
          }
          return builder.build();
      }
docs: Create a distinct list of the given args
  
  @param args elements
  @return list with distinct elements