code: @BetaApi
    public final Operation updateAccessConfigInstance(
        ProjectZoneInstanceName instance,
        String networkInterface,
        AccessConfig accessConfigResource) {
  
      UpdateAccessConfigInstanceHttpRequest request =
          UpdateAccessConfigInstanceHttpRequest.newBuilder()
              .setInstance(instance == null ? null : instance.toString())
              .setNetworkInterface(networkInterface)
              .setAccessConfigResource(accessConfigResource)
              .build();
      return updateAccessConfigInstance(request);
    }
docs: Updates the specified access config from an instance's network interface with the data included
  in the request. This method supports PATCH semantics and uses the JSON merge patch format and
  processing rules.
  
  <p>Sample code:
  
  <pre><code>
  try (InstanceClient instanceClient = InstanceClient.create()) {
  ProjectZoneInstanceName instance = ProjectZoneInstanceName.of("[PROJECT]", "[ZONE]", "[INSTANCE]");
  String networkInterface = "";
  AccessConfig accessConfigResource = AccessConfig.newBuilder().build();
  Operation response = instanceClient.updateAccessConfigInstance(instance, networkInterface, accessConfigResource);
  }
  </code></pre>
  
  @param instance The instance name for this request.
  @param networkInterface The name of the network interface where the access config is attached.
  @param accessConfigResource An access configuration attached to an instance's network
  interface. Only one access config per instance is supported.
  @throws com.google.api.gax.rpc.ApiException if the remote call fails