trezor-firmware/core/src/trezor/__init__.py

import trezorconfig as config  # noqa: F401
import trezorio as io  # noqa: F401

if False:
    import trezorio.fatfs as fatfs
else:
    # a bug in mypy causes a crash at _usage site_ of the following:
    fatfs = io.fatfs
    # hence the if False branch that does what mypy understands - but which doesn't
    # actually work because `trezorio.fatfs` is not importable.