code: @SuppressWarnings("WeakerAccess")
    public Policy setIamPolicy(String instanceId, Policy policy) {
      return ApiExceptions.callAndTranslateApiException(setIamPolicyAsync(instanceId, policy));
    }
docs: Replaces the IAM policy associated with the specified instance.
  
  <p>Sample code:
  
  <pre>{@code
  Policy newPolicy = client.setIamPolicy("my-instance",
  Policy.newBuilder()
  .addIdentity(Role.of("bigtable.user"), Identity.user("someone@example.com"))
  .addIdentity(Role.of("bigtable.admin"), Identity.group("admins@example.com"))
  .build());
  }</pre>
  
  @see <a
  href="https://cloud.google.com/bigtable/docs/access-control#iam-management-instance">Instance-level
  IAM management</a>