code: public void beginCreate(String resourceGroupName, String clusterName, String extensionName, ExtensionInner parameters) {
          beginCreateWithServiceResponseAsync(resourceGroupName, clusterName, extensionName, parameters).toBlocking().single().body();
      }
docs: Creates an HDInsight cluster extension.
  
  @param resourceGroupName The name of the resource group.
  @param clusterName The name of the cluster.
  @param extensionName The name of the cluster extension.
  @param parameters The cluster extensions create request.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @throws ErrorResponseException thrown if the request is rejected by server
  @throws RuntimeException all other wrapped checked exceptions if the request fails to be sent