Add conversion of ROOT histograms to PlottableHistogram (Sourcery refactored)

[sourcery-ai]

Pull Request #27 refactored by Sourcery.

Since the original Pull Request was opened as a fork in a contributor's
repository, we are unable to create a Pull Request branching from it.

To incorporate these changes, you can either:

1. Merge this Pull Request instead of the original, or

2. Ask your contributor to locally incorporate these commits and push them to
   the original Pull Request

   Incorporate changes via command line

   git fetch https://github.com/scikit-hep/uhi pull/27/head
   git merge --ff-only FETCH_HEAD
   git push

NOTE: As code is pushed to the original Pull Request, Sourcery will
re-run and update (force-push) this Pull Request with new refactorings as
necessary. If Sourcery finds no refactorings at any point, this Pull Request
will be closed automatically.

See our documentation here.

Run Sourcery locally

Reduce the feedback loop during development by using the Sourcery editor plugin:

• VS Code
• PyCharm

[sourcery-ai]

Sourcery Code Quality Report

✅  Merging this PR will increase code quality in the affected files by 4.67%.

Quality metrics	Before	After	Change
Complexity	3.18 ⭐	2.38 ⭐	-0.80 👍
Method Length	29.89 ⭐	26.00 ⭐	-3.89 👍
Working memory	9.24 🙂	7.89 🙂	-1.35 👍
Quality	76.70% ⭐	81.37% ⭐	4.67% 👍

Other metrics	Before	After	Change
Lines	180	270	90

Changed files	Quality Before	Quality After	Quality Change
src/uhi/numpy_plottable.py	76.70% ⭐	81.37% ⭐	4.67% 👍

Here are some functions in these files that still need a tune-up:

File	Function	Complexity	Length	Working Memory	Quality	Recommendation
src/uhi/numpy_plottable.py	ensure_plottable_histogram	13 🙂	174 😞	21 ⛔	35.33% 😞	Try splitting into smaller methods. Extract out complex expressions
src/uhi/numpy_plottable.py	_bin_helper	4 ⭐	64 🙂	10 😞	70.30% 🙂	Extract out complex expressions
src/uhi/numpy_plottable.py	ROOTPlottableHistogram.__init__	0 ⭐	60 ⭐	12 😞	71.27% 🙂	Extract out complex expressions
src/uhi/numpy_plottable.py	ROOTPlottableHistogram.variances	2 ⭐	35 ⭐	10 😞	76.92% ⭐	Extract out complex expressions

Legend and Explanation

The emojis denote the absolute quality of the code:

• ⭐ excellent
• 🙂 good
• 😞 poor
• ⛔ very poor

The 👍 and 👎 indicate whether the quality has improved or gotten worse with this pull request.

---

Please see our documentation here for details on how these metrics are calculated.

We are actively working on this report - lots more documentation and extra metrics to come!

Let us know what you think of it by mentioning @sourcery-ai in a comment.