Custom Form Validation With Caldera Forms Run Action

<?php
add_filter( 'custom_cf_validator', function ( $data ) {
    if ( array_key_exists( 'option', $data ) && 1 != $data['option'] ) {
        return array(
            'type' => 'error',
            'note' => '1 is an invalid option'
        );
    }

} );