code: public void unbindEip(UnbindEipRequest request) {
          checkStringNotEmpty(request.getEip(), "eip should not be empty");
          if (Strings.isNullOrEmpty(request.getClientToken())) {
              request.setClientToken(generateDefaultClientToken());
          }
          InternalRequest internalRequest = this.createRequest(request, HttpMethodName.PUT, request.getEip());
          internalRequest.addParameter("unbind", null);
          internalRequest.addParameter(CLIENT_TOKEN_IDENTIFY, request.getClientToken());
          internalRequest.addHeader(Headers.CONTENT_LENGTH, "0");
          internalRequest.addHeader(Headers.CONTENT_TYPE, DEFAULT_CONTENT_TYPE);
          invokeHttpClient(internalRequest, AbstractBceResponse.class);
      }
docs: unbind the eip from a specified instance
  @param request The request containing all options for unbinding eip