code: public function get($id)
      {
          if (isset($this->forms[$id])) {
              return $this->forms[$id];
          }
  
          throw new FormalException(
              "Unknown form field '$id'. Available fields are: " . implode(', ', array_keys($this->forms))
          );
      }
docs: @param string $id
  
  @return Form
  @throws FormalException