code: public function func(
          /*# string */ $function,
          /*# string */ $col,
          /*# string */ $alias = ''
      ) {
          $rawMode = $this->isRaw($col);
          if ('' === $alias) {
              $this->clause_column[] = [$rawMode, $col, $function];
          } else {
              $this->clause_column[(string) $alias] = [$rawMode, $col, $function];
          }
          return $this;
      }
docs: {@inheritDoc}