code: public Map<String, String> invokeHeaders() throws InternalException, CloudException {
          ClientAndResponse clientAndResponse = invokeInternal();
          try {
              Map<String, String> headers = new HashMap<String, String>();
              // doesn't support duplicate header keys, but they are unused by glacier
              for (Header header : clientAndResponse.response.getAllHeaders()) {
                  headers.put(header.getName().toLowerCase(), header.getValue());
              }
              return headers;
          }finally {
              clientAndResponse.client.getConnectionManager().shutdown();
          }
      }
docs: Invokes the method and returns the response headers
  @return map of response headers; duplicate header keys are ignored
  @throws InternalException
  @throws CloudException
  @throws GlacierException