The function handles bytes input, however that is never used.
The function has two callers:
1)
```
if istext(left) and istext(right):
explanation = _diff_text(left, right, verbose
```
`istext` checks `isinstance(str)`.
2)
```
def _notin_text(term: str, text: str, verbose: int = 0) -> List[str]:
...
diff = _diff_text(correct_text, text, verbose
```
and `_notin_text` is called once:
```
if istext(left) and istext(right):
explanation = _notin_text(left, right, verbose
```
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