为什么isSelected（）选项总是返回false，即使我在Gravity Forms中选中了复选框？

I implemented my Gravity Form in wordpress, and need to get status if checkbox with ID 12 is checked , or not.

add_filter( 'gform_pre_render_3', 'gw_conditional_requirement' );
add_filter( 'gform_pre_validation_3', 'gw_conditional_requirement' );
function gw_conditional_requirement( $form ) {

    foreach( $form['fields'] as &$field ) {
        if( $field['id'] == 12 ) {

            foreach($field['choices'] as $choice) {
                var_dump($choice);
            }
        }
    }
    return $form;
}

But isSelected() choice always return false. Did I do something wrong, or exists better way, how to find out if checkbox is checked, please??