Is your feature request related to a use case or problem? Please describe.
Right now a lot of modules (in particular tests) are pretty free form with how they do imports. It's a good practice to import modules wherever possible.

bad:

from cirq.devices import GridQubit

good:

from cirq import devices

devices.GridQubit(whatever)

Describe the solution you'd like
We should add a new plugin to pylint (or install an existing one) that catches non module imports where it makes sense. Some exceptions might be __init__ modules or typing imports and vendor modules that should just do import cirq everywhere.