dependants through the Python API

I'm looking for a way to do what MaxScripts's "refs.dependants" and "refs.dependson" does, but with the Python API.

So far I've figured out the "dependson" part:

for ref in my_mod.refs:
--for subref in ref.refs:

But I'd really like to know about "dependants", without traversing the whole scene and connecting the dots myself.

Sorry if this is really obvious, I'm a Max noob.

:-) Sune