@ron-unstructured reported that loading files with:
```
from unstructured.partition.pdf import partition_pdf
elements_yolox = partition_pdf(filename="1706.03762.pdf", strategy='hi_res', model_name="yolox")
print(elements_yolox)
```
Throws an error. After debugging the execution I found that the issue is
that an object of class Formula is being created, however, this class
doesn't contain an __init__ method. This PR solves the issue of adding a
constructor method with an empty string for the element.
The file can be found at:
https://drive.google.com/drive/folders/1hDumyps0hA4_d-GZxs3Hij15Cpa5fjWY?usp=sharing
After this PR is merged this file is correctly processed
* Apply import sorting
ruff . --select I --fix
* Remove unnecessary open mode parameter
ruff . --select UP015 --fix
* Use f-string formatting rather than .format
* Remove extraneous parentheses
Also use "" instead of str()
* Resolve missing trailing commas
ruff . --select COM --fix
* Rewrite list() and dict() calls using literals
ruff . --select C4 --fix
* Add () to pytest.fixture, use tuples for parametrize, etc.
ruff . --select PT --fix
* Simplify code: merge conditionals, context managers
ruff . --select SIM --fix
* Import without unnecessary alias
ruff . --select PLR0402 --fix
* Apply formatting via black
* Rewrite ValueError somewhat
Slightly unrelated to the rest of the PR
* Apply formatting to tests via black
* Update expected exception message to match
0d81564
* Satisfy E501 line too long in test
* Update changelog & version
* Add ruff to make tidy and test deps
* Run 'make tidy'
* Update changelog & version
* Update changelog & version
* Add ruff to 'check' target
Doing so required me to also fix some non-auto-fixable issues. Two of them I fixed with a noqa: SIM115, but especially the one in __init__ may need some attention. That said, that refactor is out of scope of this PR.
