private com.google.protobuf.SingleFieldBuilderV3<
            com.google.cloud.vertexai.api.CachedContent.UsageMetadata,
            com.google.cloud.vertexai.api.CachedContent.UsageMetadata.Builder,
            com.google.cloud.vertexai.api.CachedContent.UsageMetadataOrBuilder>
        getUsageMetadataFieldBuilder() {
      if (usageMetadataBuilder_ == null) {
        usageMetadataBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.cloud.vertexai.api.CachedContent.UsageMetadata,
                com.google.cloud.vertexai.api.CachedContent.UsageMetadata.Builder,
                com.google.cloud.vertexai.api.CachedContent.UsageMetadataOrBuilder>(
                getUsageMetadata(), getParentForChildren(), isClean());
        usageMetadata_ = null;
      }
      return usageMetadataBuilder_;
    }
<pre>
Output only. Metadata on the usage of the cached content.
</pre>

<code>
.google.cloud.vertexai.v1.CachedContent.UsageMetadata usage_metadata = 12 [(.google.api.field_behavior) = OUTPUT_ONLY];
</code>
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/CachedContent.java