@java.lang.Override
  public boolean containsLabels(java.lang.String key) {
    if (key == null) {
      throw new NullPointerException("map key");
    }
    return internalGetLabels().getMap().containsKey(key);
  }
<pre>
Optional. The labels with user-defined metadata for the request. It is used
for billing and reporting only.

Label keys and values can be no longer than 63 characters
(Unicode codepoints) and can only contain lowercase letters, numeric
characters, underscores, and dashes. International characters are allowed.
Label values are optional. Label keys must start with a letter.
</pre>

<code>map&lt;string, string&gt; labels = 10 [(.google.api.field_behavior) = OPTIONAL];</code>
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/GenerateContentRequest.java