code: public <T extends AbstractGoogleJsonClient.Builder> T fromApplicationDefaultCredential(T builder) {
      Preconditions.checkNotNull(builder);
      return fromCredential(builder, CredentialFactory.getApplicationDefaultCredential());
    }
docs: Prepare an AbstractGoogleJsonClient.Builder using the Application Default Credential.
  
  @param builder The builder to be prepared.
  @return The passed in builder, for easy chaining.