code: public function isValid(array $values)
      {
          $this->errorMessages = [];
          
          foreach ($this->elements->getElements() as $element) {
              $elementId = $element->getID();
              if (empty($elementId)) {
                  continue;
              }
              
              $value = null;
              if (array_key_exists($elementId, $values)) {
                  $value = $values[$elementId];
              }
              $element->setValue($value);
              
              $this->filterElement($element);
              $this->validateElement($element);
          }
          
          return count($this->errorMessages) === 0;
      }
docs: Validates all the elements against the defined validators.
  
  During validation the given values will be set as the new values of the elements.
  
  @param array $values
  @return bool