A jog around the park!

    def element(self, uri, idx=None):
        _path = uri.split('/')
        if not _path:
            return None

        def get_indexes(_idx):
            indexes = []
            if _idx is None:
                indexes = [0]
            elif isinstance(_idx, int):
                indexes = [_idx]
            elif isinstance(_idx, tuple):
                indexes = list(_idx)
            elif isinstance(_idx, list):
                indexes = _idx

            cnt = len(_path)
            if cnt > len(indexes):
                for i in range(0, cnt-1):
                    indexes.insert(0, 0)
            return indexes

        def get_element(parent, elm_type, elm_id):
            def walk(_parent):
                for node in _parent.nodes.values():
                    if node.type == elm_type and node.id == elm_id:
                        return node
                    if node.has_children:
                        node = walk(node)
                        if node:
                            return node
                return None
            return walk(parent)

        idxs = get_indexes(idx)
        _type = _path.pop(0)
        _id = f'{_type.lower()}{idxs.pop(0)}'

        elm = get_element(self, _type, _id)
        if elm.uri == uri:
            return elm

        while idxs:
            _type = _path.pop(0)
            _id = f'{_type.lower()}{idxs.pop(0)}'
            elm = get_element(elm, _type, _id)
        return elm