Docformatter inconsistency

[pedropgusmao]

There seems to be a conflict between docformatter and linter.s

When running dev/fnt.sh with the following code snipped the linter will complain that the code has an extra whitespace before ':'.
However, if the whitespace is manually removed from the source-code, then it is put back by the document formatter.

266     list_samples_per_class: List[List[np.ndarray]] = [
267         x_l[boundaries[idx] : boundaries[idx + 1]] for idx in range(num_classes)
268     ]

Running dev/fnt.sh:

Format code and run all test scripts
Fixing /home/pedro/repos/flower_2/src/py/flwr_example/pytorch_save_weights/client.py
Skipped 1 files
=== test.sh ===
- clang-format: done
Skipped 1 files
- isort:  done
All done! ✨ 🍰 ✨
58 files would be left unchanged.
- black:  done
- docformatter:  done
Success: no issues found in 154 source files
- mypy:   done

--------------------------------------------------------------------
Your code has been rated at 10.00/10 (previous run: 10.00/10, +0.00)

- pylint: done
src/py/flwr/dataset/utils/common.py:267:28: E203 whitespace before ':'

[pedropgusmao]

Related: psf/black#279