code: public static DeleteFollowRequest checkRequest(
  			final HttpServletRequest request,
  			final DeleteRequest deleteRequest,
  			final DeleteFollowResponse deleteFollowResponse) {
  		final Node user = checkUserIdentifier(request, deleteFollowResponse);
  		if (user != null) {
  			final Node followed = checkFollowedIdentifier(request,
  					deleteFollowResponse);
  			if (followed != null) {
  				return new DeleteFollowRequest(deleteRequest.getType(), user,
  						followed);
  			}
  		}
  
  		return null;
  	}
docs: check a delete follow edge request for validity concerning NSSP
  
  @param request
  Tomcat servlet request
  @param deleteRequest
  basic delete request object
  @param deleteFollowResponse
  delete follow edge response object
  @return delete follow edge request object<br>
  <b>null</b> if the delete follow edge request is invalid