code: @BetaApi
    public final Operation patchAutoscaler(
        String autoscaler,
        ProjectZoneName zone,
        Autoscaler autoscalerResource,
        List<String> fieldMask) {
  
      PatchAutoscalerHttpRequest request =
          PatchAutoscalerHttpRequest.newBuilder()
              .setAutoscaler(autoscaler)
              .setZone(zone == null ? null : zone.toString())
              .setAutoscalerResource(autoscalerResource)
              .addAllFieldMask(fieldMask)
              .build();
      return patchAutoscaler(request);
    }
docs: Updates an autoscaler in the specified project using 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 (AutoscalerClient autoscalerClient = AutoscalerClient.create()) {
  String autoscaler = "";
  ProjectZoneName zone = ProjectZoneName.of("[PROJECT]", "[ZONE]");
  Autoscaler autoscalerResource = Autoscaler.newBuilder().build();
  List&lt;String&gt; fieldMask = new ArrayList&lt;&gt;();
  Operation response = autoscalerClient.patchAutoscaler(autoscaler, zone, autoscalerResource, fieldMask);
  }
  </code></pre>
  
  @param autoscaler Name of the autoscaler to patch.
  @param zone Name of the zone for this request.
  @param autoscalerResource Represents an Autoscaler resource. Autoscalers allow you to
  automatically scale virtual machine instances in managed instance groups according to an
  autoscaling policy that you define. For more information, read Autoscaling Groups of
  Instances. (== resource_for beta.autoscalers ==) (== resource_for v1.autoscalers ==) (==
  resource_for beta.regionAutoscalers ==) (== resource_for v1.regionAutoscalers ==)
  @param fieldMask The fields that should be serialized (even if they have empty values). If the
  containing message object has a non-null fieldmask, then all the fields in the field mask
  (and only those fields in the field mask) will be serialized. If the containing object does
  not have a fieldmask, then only non-empty fields will be serialized.
  @throws com.google.api.gax.rpc.ApiException if the remote call fails