code: public static PredictionEndpoint authenticate(RestClient restClient, final String apiKey) {
          return new PredictionEndpointImpl(restClient).withApiKey(apiKey);
      }
docs: Initializes an instance of Custom Vision Prediction API client.
  
  @param restClient the REST client to connect to Azure.
  @param apiKey the Custom Vision Prediction API key
  @return the Custom Vision Prediction API client