* Added function that checks if a string is an isogram.
* Added wiki reference and fixed comments.
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
* Made function name more self-documenting. Raise ValueError if string contains 1 or more digits. Renamed file. Lowercase string inside function.
* Removed check_isogram.py (file renamed).
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
* Fixed test failure.
* Raise ValueError when string has non-alpha characters. Removed import.
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
