code: public static Filter createFilterFromFilterSpec(Request request, String filterSpec)
              throws FilterFactory.FilterNotCreatedException {
          Description topLevelDescription = request.getRunner().getDescription();
          String[] tuple;
  
          if (filterSpec.contains("=")) {
              tuple = filterSpec.split("=", 2);
          } else {
              tuple = new String[]{ filterSpec, "" };
          }
  
          return createFilter(tuple[0], new FilterFactoryParams(topLevelDescription, tuple[1]));
      }
docs: Creates a {@link Filter}.
  
  A filter specification is of the form "package.of.FilterFactory=args-to-filter-factory" or
  "package.of.FilterFactory".
  
  @param request the request that will be filtered
  @param filterSpec the filter specification
  @throws org.junit.runner.FilterFactory.FilterNotCreatedException