python Tree 若干相关问题

1. Tree traverse:
@ path string to node/value map
@ path sequence to node/value map
@ list of nodes/values (reference)
@ deep list of nodes?
\==> 2

2. Tree 和 deep dict 两者之间的一致性及其体现(基本原理及设计思想)
计入设计文档

3. Tree search:
@ include/exclude
@ return string or list sequence map
@ copy or assign?
@ key indexed items

4. Tree node value copy/deepcopy?
\==> python mutable/immutable 设计思想？

5. add operation:
head.branch + root.br1 ?
head.branch + {['root', 'br1', 'br11'] : value1, ['root', 'br1', 'br12'] : value2, ...}
\==> Tree update

6. Tree cyclic link 问题