public com.google.protobuf.Duration getTravelDuration() {
      if (travelDurationBuilder_ == null) {
        return travelDuration_ == null
            ? com.google.protobuf.Duration.getDefaultInstance()
            : travelDuration_;
      } else {
        return travelDurationBuilder_.getMessage();
      }
    }
<pre>
Required. The maximum travel time in seconds. The maximum allowed value is
`3600s` (one hour). Format is `123s`.
</pre>

<code>
.google.protobuf.Duration travel_duration = 3 [(.google.api.field_behavior) = REQUIRED];
</code>

@return The travelDuration.
java-talent/proto-google-cloud-talent-v4/src/main/java/com/google/cloud/talent/v4/CommuteFilter.java