code: protected void registerComponents(final ClassScanner componentScanner, final Class<?> scanningRoot) {
          componentScanners.add(new Pair<Class<?>, ClassScanner>(scanningRoot, componentScanner));
      }
docs: Can be called only before {@link #create()} is invoked.
  
  @param componentScanner used to scan for annotated classes.
  @param scanningRoot root of the scanning.