/**
  * {@inheritdoc}
  * 
  * 
  */
 public function submitForm(array &$form, FormStateInterface $form_state)
 {
     $c = new Conversion();
     $val = $form_state->getValue('length');
     $from = $form_state->getValue('unit');
     $to = $form_state->getValue('units');
     print_r('input');
     print_r($val);
     //$result = $c->assign($from,$val);
     drupal_set_message($this->t('Your result is @length @unit', array('@length' => $c->convertlength($from, $val, $to), '@unit' => $form_state->getValue('units'))));
 }