Support for nested array & dict in DictMod of fireworks?

Dear Developers,

I find the dict mod syntax a very powerful tool for chaining fireworks / firetasks. However it seems the current implementation does not correctly handle the nested array and dict situations, while the same syntax is supported by Mongo standard (If I’m not mistaken).

What I want to achieve:
Firework 1 → FWAction(mod_spec={"_set": {"_tasks->0->param1": value}}) → Firework 2

when firework 1 changes some parameters in one specific task of firework 2 (in addition to fw_spec).

The key _tasks->0->param1 is supposed to be equivalent to _tasks.0.param1 in mongo standard. However the current Fireworks implementation will raise error

TypeError: list indices must be integers or slices, not str

because the expression is translated to fw_spec["_tasks"]["0"]["param1"] instead of fw_spec["_tasks"][0]["param1"] (in fireworks/utilities/

I think in most cases the integer inside the string should be interpreted as index instead of key. Is it ok to change the behavior of get_nested_dict in