Group
Groups are visual containers of elements. They do not contain any data and other elements may be moved in and out of them. Here's how you add them:
$form->addElement('column_1', array(
Specs::TYPE => 'group',
Specs::ATTRIBUTES => ['class' => 'col-md-6 col-sm-12']
));
In order to specify that an element belongs visually to a group you must set its group property.
$form->addElement('email', array(
Specs::TYPE => 'email',
Specs::LABEL => 'Email address',
Specs::GROUP => 'column_1'
));