/** Creates {@link CloseableHttpAsyncClient} instance with default configuration. */
 public static CloseableHttpAsyncClient createDefault() {
   return HttpAsyncClientBuilder.create().build();
 }
 /**
  * Creates {@link CloseableHttpAsyncClient} instance with default configuration based on ssytem
  * properties.
  */
 public static CloseableHttpAsyncClient createSystem() {
   return HttpAsyncClientBuilder.create().useSystemProperties().build();
 }
 /**
  * Creates builder object for construction of custom {@link CloseableHttpAsyncClient} instances.
  */
 public static HttpAsyncClientBuilder custom() {
   return HttpAsyncClientBuilder.create();
 }