@CanIgnoreReturnValue
    public Builder setVertexAi(VertexAI vertexAi) {
      checkNotNull(vertexAi, "VertexAI can't be null.");
      this.vertexAi = vertexAi;
      return this;
    }
Sets {@link com.google.cloud.vertexai.VertexAI} that contains the default configs for the
generative model. This is required for building a GenerativeModel instance.
java-vertexai/google-cloud-vertexai/src/main/java/com/google/cloud/vertexai/generativeai/GenerativeModel.java