code: @SuppressWarnings("unused")
      public static Builder newBuilder(@NonNull Auth0 account, @NonNull LockCallback callback) {
          return new PasswordlessLock.Builder(account, callback);
      }
docs: Creates a new Lock.Builder instance with the given account and callback.
  Use of Passwordless connections requires your Application to have the <b>Resource Owner</b> Legacy Grant Type enabled.
  See <a href="https://auth0.com/docs/clients/client-grant-types">Client Grant Types</a> to learn how to enable it.
  
  @param account  details to use against the Auth0 Authentication API.
  @param callback that will receive the authentication results.
  @return a new Lock.Builder instance.