code: @SuppressWarnings("resource")
      @Override
      public InputStream retrieveExternalContent(final URI sourceUri) throws IOException {
          final HttpGet httpGet = new HttpGet(sourceUri);
          final CloseableHttpClient client = getCloseableHttpClient();
          final HttpResponse response = client.execute(httpGet);
          return response.getEntity().getContent();
      }
docs: Retrieve the content at the URI using the global connection pool.
  @param sourceUri the source uri
  @return the content at the URI using the global connection pool
  @throws IOException if IO exception occurred