Document possible input.

Author: vmcj

webapp/src/Service/ImportProblemService.php

@@ -1200,6 +1200,10 @@ public static function parseTestCaseGroupMeta(string $fileContent, string $name,
     }
 
     /**
+     * Allow to import the types both as arrays and as strings. Due
+     * to the recursion to make parsing of the strings easier this now
+     * also works for arrays inside arrays.
+     *
      * @param string|array<mixed, mixed> $input
      * @return string[]
      */