public Builder mergeExpireTime(com.google.protobuf.Timestamp value) {
      if (expireTimeBuilder_ == null) {
        if (expirationCase_ == 2
            && expiration_ != com.google.protobuf.Timestamp.getDefaultInstance()) {
          expiration_ =
              com.google.protobuf.Timestamp.newBuilder((com.google.protobuf.Timestamp) expiration_)
                  .mergeFrom(value)
                  .buildPartial();
        } else {
          expiration_ = value;
        }
        onChanged();
      } else {
        if (expirationCase_ == 2) {
          expireTimeBuilder_.mergeFrom(value);
        } else {
          expireTimeBuilder_.setMessage(value);
        }
      }
      expirationCase_ = 2;
      return this;
    }
<pre>
Desired expiration time of the access token. This value must
be at most 24 hours in the future. If a value is not specified, the
token's expiration time will be set to a default value of 1 hour in the
future.
</pre>

<code>.google.protobuf.Timestamp expire_time = 2;</code>
java-workstations/proto-google-cloud-workstations-v1beta/src/main/java/com/google/cloud/workstations/v1beta/GenerateAccessTokenRequest.java