class CollectionReference extends Query {

  CollectionReference(ResourcePath path, FirebaseFirestore firestore) {
    super(com.google.firebase.firestore.core.Query.atPath(path), firestore);
    if (path.length() % 2 != 1) {
      throw new IllegalArgumentException(
          "Invalid collection reference. Collection references must have an odd number "
              + "of segments, but "
              + path.canonicalString()
              + " has "
              + path.length());
    }
  }

    CollectionReference(ResourcePath path, FirebaseFirestore firestore);

}