code: public ServiceFuture<PolicyAssignmentInner> getByIdAsync(String policyAssignmentId, final ServiceCallback<PolicyAssignmentInner> serviceCallback) {
          return ServiceFuture.fromResponse(getByIdWithServiceResponseAsync(policyAssignmentId), serviceCallback);
      }
docs: Gets a policy assignment by ID.
  When providing a scope for the assigment, use '/subscriptions/{subscription-id}/' for subscriptions, '/subscriptions/{subscription-id}/resourceGroups/{resource-group-name}' for resource groups, and '/subscriptions/{subscription-id}/resourceGroups/{resource-group-name}/providers/{resource-provider-namespace}/{resource-type}/{resource-name}' for resources.
  
  @param policyAssignmentId The ID of the policy assignment to get. Use the format '/{scope}/providers/Microsoft.Authorization/policyAssignments/{policy-assignment-name}'.
  @param serviceCallback the async ServiceCallback to handle successful and failed responses.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the {@link ServiceFuture} object