code: public <V> ResultTransformer<List<V>> list(Expression<V> expression) {
          final Expression<V> lookup = getLookup(expression);
          return new GroupByList<K, V>(key, expression) {
              @Override
              protected V transform(Group group) {
                  return group.getOne(lookup);
              }
          };
      }
docs: Get the results as a list
  
  @param expression projection
  @return new result transformer