code: public function hasSubmit(SelectorInterface $selector)
      {
          foreach ($this->buttons as $button) {
              if ($selector->isMatch($button)) {
                  return true;
              }
          }
  
          return false;
      }
docs: Test to see if a form has a submit button.
  
  @param $selector Criteria to apply.
  
  @return bool True if present.