计算数据结构的md5哈希

I want to compute an md5 hash not of a string, but of an entire data structure. I understand the mechanics of a way to do this (dispatch on the type of the value, canonicalize dictionary key order and other randomness, recurse into sub-values, etc). But it seems like the kind of operation that would be generally useful, so I'm surprised I need to roll this myself. I want to compute an md5 hash not of a string,