public async Task SetIamPolicyAsync()
        {
            // Snippet: SetIamPolicyAsync(string,Policy,CallSettings)
            // Additional: SetIamPolicyAsync(string,Policy,CancellationToken)
            // Create client
            PublisherClient publisherClient = PublisherClient.Create();
            // Initialize request argument(s)
            string formattedResource = PublisherClient.FormatTopicName("[PROJECT]", "[TOPIC]");
            Policy policy            = new Policy();
            // Make the request
            Policy response = await publisherClient.SetIamPolicyAsync(formattedResource, policy);

            // End snippet
        }
        public async Task SetIamPolicyAsync_RequestObject()
        {
            // Snippet: SetIamPolicyAsync(SetIamPolicyRequest,CallSettings)
            // Create client
            PublisherClient publisherClient = await PublisherClient.CreateAsync();

            // Initialize request argument(s)
            SetIamPolicyRequest request = new SetIamPolicyRequest
            {
                Resource = new TopicName("[PROJECT]", "[TOPIC]").ToString(),
                Policy   = new Policy(),
            };
            // Make the request
            Policy response = await publisherClient.SetIamPolicyAsync(request);

            // End snippet
        }