private com.google.protobuf.SingleFieldBuilderV3<
            com.google.protobuf.Timestamp,
            com.google.protobuf.Timestamp.Builder,
            com.google.protobuf.TimestampOrBuilder>
        getExpireTimeFieldBuilder() {
      if (expireTimeBuilder_ == null) {
        if (!(expirationCase_ == 9)) {
          expiration_ = com.google.protobuf.Timestamp.getDefaultInstance();
        }
        expireTimeBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.protobuf.Timestamp,
                com.google.protobuf.Timestamp.Builder,
                com.google.protobuf.TimestampOrBuilder>(
                (com.google.protobuf.Timestamp) expiration_, getParentForChildren(), isClean());
        expiration_ = null;
      }
      expirationCase_ = 9;
      onChanged();
      return expireTimeBuilder_;
    }
<pre>
Timestamp of when this resource is considered expired.
This is *always* provided on output, regardless of what was sent
on input.
</pre>

<code>.google.protobuf.Timestamp expire_time = 9;</code>
java-vertexai/proto-google-cloud-vertexai-v1/src/main/java/com/google/cloud/vertexai/api/CachedContent.java