Added string return type to build_full_ai_prompt function

question.php

@@ -188,7 +188,7 @@ public function grade_response(array $response) : array {
      * @param string $markscheme
      * @return string;
      */
-    public function build_full_ai_prompt($response, $aiprompt, $defaultmark, $markscheme) {
+    public function build_full_ai_prompt($response, $aiprompt, $defaultmark, $markscheme): string {
         $responsetext = strip_tags($response);
             $responsetext = '[['.$responsetext.']]';
             $prompt = get_config('qtype_aitext', 'prompt');