code: public final Policy getIamPolicy(String resource) {
  
      GetIamPolicyRequest request = GetIamPolicyRequest.newBuilder().setResource(resource).build();
      return getIamPolicy(request);
    }
docs: Gets the access control policy for an instance resource. Returns an empty policy if an instance
  exists but does not have a policy set.
  
  <p>Authorization requires `spanner.instances.getIamPolicy` on
  [resource][google.iam.v1.GetIamPolicyRequest.resource].
  
  <p>Sample code:
  
  <pre><code>
  try (InstanceAdminClient instanceAdminClient = InstanceAdminClient.create()) {
  String formattedResource = InstanceName.format("[PROJECT]", "[INSTANCE]");
  Policy response = instanceAdminClient.getIamPolicy(formattedResource);
  }
  </code></pre>
  
  @param resource REQUIRED: The resource for which the policy is being requested. `resource` is
  usually specified as a path. For example, a Project resource is specified as
  `projects/{project}`.
  @throws com.google.api.gax.rpc.ApiException if the remote call fails