Add a nested_callable and getcallable util

[muellerzr]

nested_callable + getcallable

What does this add?

This PR adds a small util func of nested_callable. I was noticing this pattern being repeated a lot in fastai code:

someresult = getattr(obj, name, noop)(arg_a, arg_b, arg_c)

This util simplifies that code with a shorthand of nested_callable for nested attributes, and getcallable for non-nested attributes.

The new version looks like so:

someresult = nested_callable(obj, name)(arg_a, arg_b, arg_c)

(And with getcallable):

someresult = getcallable(obj, name)(arg_a, arg_b, arg_c)

cc @hamelsmu @jph00

[review-notebook-app]

Check out this pull request on 

See visual diffs & provide feedback on Jupyter Notebooks.

---

Powered by ReviewNB

[hamelsmu]

LGTM