code: protected function getGroupsForStep($step)
      {
          $groups = ['Default'];
  
          if ($step === static::CHECKOUT_STEP) {
              $groups[] = 'Checkout';
              $groups[] = 'Identity';
              $groups[] = 'Availability';
          } elseif ($step === static::SHIPMENT_STEP) {
              $groups[] = 'Availability';
          }
  
          return $groups;
      }
docs: Returns the validation groups for the given step.
  
  @param string $step
  
  @return array