* @param $valueInstance An object instance which can provide "field values"
* @return void
*/
- public final function addValueInstance ($variableName, FrameworkInterface $valueInstance) {
+ public final function addValueInstance (string $variableName, FrameworkInterface $valueInstance) {
$this->setGenericArrayElement('recipients', $this->getTemplateName(), 'values', $variableName, $valueInstance);
}