diff --git a/helpers/Toolbox.ts b/helpers/Toolbox.ts
index cda569340b7ec53d906e353555fa289fa920d9b8..d0fbfd5e26a97250a8232ba2b5f05ae9121be92e 100644
--- a/helpers/Toolbox.ts
+++ b/helpers/Toolbox.ts
@@ -51,6 +51,10 @@ class Toolbox {
     public getKeysWithPrefix(obj: object, prefix: string): Array<string> {
         return Object.keys(obj).filter(key => key.startsWith(prefix));
     }
+
+    public isString(value: unknown): value is string {
+        return typeof value === 'string' || value instanceof String;
+    }
 }