private static Content fromStringWithRole(String role, String text) {
    checkArgument(!Strings.isNullOrEmpty(text), "text message can't be null or empty.");
    return Content.newBuilder().addParts(Part.newBuilder().setText(text)).setRole(role).build();
  }
Creates a ContentMakerForRole for a given role.

@param role Currently accepted role values are: "user", "model". No need to call forRole for
    the "user" role since it's the default role.
java-vertexai/google-cloud-vertexai/src/main/java/com/google/cloud/vertexai/generativeai/ContentMaker.java