code: protected Factory resolveFactory(Object name, Map attributes, Object value) {
          getProxyBuilder().getContext().put(CHILD_BUILDER, getProxyBuilder());
          return getProxyBuilder().getFactories().get(name);
      }
docs: This is a hook for subclasses to plugin a custom strategy for mapping
  names to factories.
  
  @param name       the name of the factory
  @param attributes the attributes from the node
  @param value      value arguments from te node
  @return the Factory associated with name.<br>