code: private static void addProcessors(final Processor processor, final String... keys) throws IllegalStateException {
          for (final String key : keys) {
              addProcessor(key, processor);
          }
      }
docs: Adds the given {@link Processor} with the given keys to the map.
  
  @param keys The keys.
  @param processor The {@link Processor} to add.
  @throws IllegalStateException If the key already exists.