@InternalApi
  static Optional<String> getEnvironmentVariable(String envKey) {
    return Optional.ofNullable(System.getenv(envKey));
  }
This class holds default settings and credentials to make Vertex AI API calls.

<p><b>Note:</b> The VertexAI instance will start a service client when the first API call is
made. Please close the VertexAI instance after making any API calls so that clients get closed as
well.

<pre>{@code
try (VertexAI vertexAi = new VertexAI("my-project", "us-central1"); ) {
  GenerativeModel model = new GenerativeModel("gemini-pro", vertexAi)
  // Do something with the model.
}
}</pre>
java-vertexai/google-cloud-vertexai/src/main/java/com/google/cloud/vertexai/VertexAI.java