@BetaApi
  public CountTokensResponse countTokens(String text) throws IOException {
    return countTokens(ContentMaker.fromString(text));
  }
Counts tokens in a text message.

@param text a text message to count tokens
@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