Not clear how to import `image_diff`

[mccalluc]

Sorry if I'm missing something, but where are image_diff and image_regression defined or imported in this example?

from typing import Union
from PIL import Image


def test_compare(image_diff):
    image: Image or str or bytes = Image.new()
    image2: Image or str or bytes = '/path/to/image.jpeg'
    image_diff(image, image2)


def test_regression(image_regression):
    image: Union[Image, str, bytes] = Image.new()
    image_regression(image, threshold=0.5)

Depending on how I import and use it I can get this error:

Fixture "image_diff" called directly. Fixtures are not meant to be called directly,
but are created automatically when test functions request them as parameters.

or

TypeError: 'module' object is not callable