code: public <T extends AbstractGoogleJsonClient.Builder> T fromApiKey(T builder, String apiKey) {
      Preconditions.checkNotNull(builder);
      Preconditions.checkNotNull(apiKey);
      return prepareBuilder(builder, null, new CommonGoogleClientRequestInitializer(apiKey));
    }
docs: Prepare an AbstractGoogleJsonClient.Builder using an API key.
  
  @param builder The builder to be prepared.
  @param apiKey The API key of the Google Cloud Platform project.
  @return The passed in builder, for easy chaining.