code: public void asyncDelete(final String url, final Callback callback) {
  		final String url2 = requireNonNull(trimToNull(url), "A non-empty URL expected");
  		requireNonNull(callback, "A valid callback expected");
  		// prepare request
  		final Request request = new Request.Builder().url(url2).delete().build();
  		// submit request
  		client.newCall(request).enqueue(callback);
  	}
docs: Delete HTTP method.
  @param url - URL target of this request
  @param callback - is called back when the response is readable