ArrowStringArray: delay/conditionally import pyarrow.compute
We currently check if pyarrow is available (and a sufficiently recent version), and if that's the case, simply import `pyarrow.compute`:

https://github.com/pandas-dev/pandas/blob/3fe8e24a17170ad2296ecd81ba60e23cee763173/pandas/core/arrays/string_arrow.py#L63-L65

However, in theory, it is possible to have a pyarrow installation without `pyarrow.compute` support (it's an optional component when building). In that case the `import pyarrow.compute as pc` import will fail giving a slightly confusing error message + it will fail on a basic import of pandas (even without using any pyarrow functionality). 