message: Fix the double typeguards
  removes the typeguards from utils.ts
diff: @@ -86,19 +86,3 @@ export function getClassForDocument(document: mongoose.Document): any {
  const modelName = (document.constructor as mongoose.Model<typeof document>).modelName;
  return constructors[modelName];
  }
  -
  -/**
  - * Check if the given document is already populated
  - * @param doc The Ref with uncertain type
  - */
  -export function isDocument<T>(doc: Ref<T>): doc is InstanceType<T> {
  - return doc instanceof mongoose.Model;
  -}
  -
  -/**
  - * Check if the given array is already populated
  - * @param docs The Array of Refs with uncertain type
  - */
  -export function isDocumentArray<T>(docs: Ref<T>[]): docs is InstanceType<T>[] {
  - return Array.isArray(docs) && docs.every(v => isDocument(v));
  -}
  