src/Form/SummaryFormButtonsFieldset.php
public function setAttribute($key, $value)
    {
        if ('id' == $key) {
            $this->setFormId($value);
        }
        return parent::setAttribute($key, $value);
    }
public function setAttribute($key, $value)
    {
        if ('id' == $key) {
            $this->setFormId($value);
        }
        return parent::setAttribute($key, $value);
    }
Set Attribute

@param string $key
@param mixed  $value
@return \Zend\Form\Element|\Zend\Form\ElementInterface