code: @Beta
    public static GoogleCredential getApplicationDefault(
        HttpTransport transport, JsonFactory jsonFactory) throws IOException {
      Preconditions.checkNotNull(transport);
      Preconditions.checkNotNull(jsonFactory);
      return defaultCredentialProvider.getDefaultCredential(transport, jsonFactory);
    }
docs: {@link Beta} <br/>
  Returns the Application Default Credentials.
  
  <p>Returns the Application Default Credentials which are credentials that identify and
  authorize the whole application. This is the built-in service account if running on Google
  Compute Engine or the credentials file from the path in the environment variable
  GOOGLE_APPLICATION_CREDENTIALS.</p>
  
  @param transport the transport for Http calls.
  @param jsonFactory the factory for Json parsing and formatting.
  @return the credential instance.
  @throws IOException if the credential cannot be created in the current environment.