Use of undeclared module polars_arrow

[sclamons]

Building a clean project with pyo3-polars=0.20.0 using the polars_expr macro results in an error like the following:

error[E0433]: failed to resolve: use of undeclared crate or module `polars_arrow`
  --> src/expressions.rs:10:1
   |
10 | #[polars_expr(output_type=UInt32Type)]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ use of undeclared crate or module `polars_arrow`
   |
   = note: this error originates in the attribute macro `polars_expr` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0599]: no variant or associated item named `UInt32Type` found for enum `DataType` in the current scope
  --> src/expressions.rs:10:27
   |
10 | #[polars_expr(output_type=UInt32Type)]
   |                           ^^^^^^^^^^ variant or associated item not found in `DataType`

Some errors have detailed explanations: E0433, E0599.
For more information about an error, try `rustc --explain E0433`.
error: could not compile `polars_seqtools` (lib) due to 2 previous errors

It looks like this commit changed how pyo3-polars-derive/src/lib.rs calls into arrow, but doesn't add the import required for that change to work.

[sclamons]

A workaround is to add use polars_arrow; to the file where polars_expr is used.