public Builder addHelpLinks(int index, com.google.rpc.Help.Link value) {
      if (helpLinksBuilder_ == null) {
        if (value == null) {
          throw new NullPointerException();
        }
        ensureHelpLinksIsMutable();
        helpLinks_.add(index, value);
        onChanged();
      } else {
        helpLinksBuilder_.addMessage(index, value);
      }
      return this;
    }
<pre>
Output only. URL(s) pointing to additional information on handling the
current error.
</pre>

<code>
repeated .google.rpc.Help.Link help_links = 4 [(.google.api.field_behavior) = OUTPUT_ONLY];
</code>
java-vmmigration/proto-google-cloud-vmmigration-v1/src/main/java/com/google/cloud/vmmigration/v1/MigrationError.java