How to debug Python import failure

I have a directory structure:

network/__init__.py
network/model.py
network/transformer/__init__.py
network/transformer/t_model.py

both __init__.py files have appropriate

__all__ = [
    "model",  # or "t_model" in the case of transformer
    "view",
    ]

In t_model.py, I have

from .. import model

but it says:

ImportError: cannot import name model

If I try

from ..model import Node

it says:

ImportError: cannot import name Node

These are very confusing errors.

Edit: Even an absolute import fails:

import network as N
print(dir(N), N.__all__)
import network.model as M

['__all__', '__builtins__', '__doc__', '__file__', '__name__', '__package__', '__path__', 'transformer'] ['model', 'view']
Traceback (most recent call last):..........
AttributeError: 'module' object has no attribute 'model'

Edit: It was a circular import.