public Builder clearTtl() {
      if (ttlBuilder_ == null) {
        if (expirationCase_ == 3) {
          expirationCase_ = 0;
          expiration_ = null;
          onChanged();
        }
      } else {
        if (expirationCase_ == 3) {
          expirationCase_ = 0;
          expiration_ = null;
        }
        ttlBuilder_.clear();
      }
      return this;
    }
<pre>
Desired lifetime duration of the access token. This value must
be at most 24 hours. If a value is not specified, the token's lifetime
will be set to a default value of 1 hour.
</pre>

<code>.google.protobuf.Duration ttl = 3;</code>
java-workstations/proto-google-cloud-workstations-v1/src/main/java/com/google/cloud/workstations/v1/GenerateAccessTokenRequest.java