private CountTokensResponse countTokensFromRequest(CountTokensRequest request)
      throws IOException {
    return vertexAi.getLlmUtilityClient().countTokens(request);
  }
Sends CountTokensRequest given a request message.

@param request a {@link com.google.cloud.vertexai.api.CountTokensRequest} that contains a list
    of contents
@return a {@link com.google.cloud.vertexai.api.CountTokensResponse} instance that contains the
    total tokens and total billable characters of the given list of contents
@throws IOException if an I/O error occurs while making the API call
java-vertexai/google-cloud-vertexai/src/main/java/com/google/cloud/vertexai/generativeai/GenerativeModel.java