code: @BetaApi
    public final Operation addSignedUrlKeyBackendBucket(
        ProjectGlobalBackendBucketName backendBucket, SignedUrlKey signedUrlKeyResource) {
  
      AddSignedUrlKeyBackendBucketHttpRequest request =
          AddSignedUrlKeyBackendBucketHttpRequest.newBuilder()
              .setBackendBucket(backendBucket == null ? null : backendBucket.toString())
              .setSignedUrlKeyResource(signedUrlKeyResource)
              .build();
      return addSignedUrlKeyBackendBucket(request);
    }
docs: Adds a key for validating requests with signed URLs for this backend bucket.
  
  <p>Sample code:
  
  <pre><code>
  try (BackendBucketClient backendBucketClient = BackendBucketClient.create()) {
  ProjectGlobalBackendBucketName backendBucket = ProjectGlobalBackendBucketName.of("[PROJECT]", "[BACKEND_BUCKET]");
  SignedUrlKey signedUrlKeyResource = SignedUrlKey.newBuilder().build();
  Operation response = backendBucketClient.addSignedUrlKeyBackendBucket(backendBucket, signedUrlKeyResource);
  }
  </code></pre>
  
  @param backendBucket Name of the BackendBucket resource to which the Signed URL Key should be
  added. The name should conform to RFC1035.
  @param signedUrlKeyResource Represents a customer-supplied Signing Key used by Cloud CDN Signed
  URLs
  @throws com.google.api.gax.rpc.ApiException if the remote call fails