def create_node(content, type=None):
    global _start_node
    global _end_node
    node = Node(content)
    node.type = type
    if (_start_node is None):
        _start_node = node
    if _end_node:
        node.last = _end_node
        _end_node.next = node
    _end_node = node
    return node
def create_node(content, type=None):
    global _start_node
    global _end_node
    node = Node(content)
    node.type = type
    if (_start_node is None):
        _start_node = node
    if _end_node:
        node.last = _end_node
        _end_node.next = node
    _end_node = node
    return node