'The default contructor. Extends `NestedObjectStore`.'

def __init__(self, config, config_xml=None, fsmon=False):

    super(HierarchicalObjectStore, self).__init__(config, config_xml=config_xml)
    self.backends = odict()
    for b in sorted(config_xml.find('backends'), key=(lambda b: int(b.get('order')))):
        self.backends[int(b.get('order'))] = build_object_store_from_config(config, fsmon=fsmon, config_xml=b)
