Devise\Pages\Fields\FieldsRepository::findFieldByGlobalKeyAndLanguage PHP Method

    public function findFieldByGlobalKeyAndLanguage($key, $languageId)
    {
        return $this->GlobalField->where('key', $key)->where('language_id', $languageId)->first();
    }

 /**
  * Changes this page field to a global field
  *
  * @param  array    $fieldInput
  * @param  array    $pageInput
  * @return DvsGlobalField
  */
 protected function changeToGlobalField($fieldInput, $pageInput)
 {
     $field = $this->FieldsRepository->findFieldByGlobalKeyAndLanguage($fieldInput['key'], $pageInput['language_id']);
     if (!$field) {
         $field = $this->newGlobalField($pageInput['language_id'], $fieldInput['key'], $fieldInput['type'], $fieldInput['human_name']);
         $this->removePristinePageFields($fieldInput['key']);
     }
     return $field;
 }