refactor: simplify cast expression in PyExpr and remove unused module reference

Author: kosiew

src/expr.rs

@@ -315,10 +315,7 @@ impl PyExpr {
     pub fn cast(&self, to: PyDataType) -> PyExpr {
         // self.expr.cast_to() requires DFSchema to validate that the cast
         // is supported, omit that for now
-        let expr = Expr::Cast(Cast::new(
-            Box::new(self.expr.clone()),
-            to.data_type,
-        ));
+        let expr = Expr::Cast(Cast::new(Box::new(self.expr.clone()), to.data_type));
         expr.into()
     }
 

src/lib.rs

@@ -48,7 +48,6 @@ pub mod expr;
 #[allow(clippy::borrow_deref_ref)]
 mod functions;
 pub mod physical_plan;
-mod pyarrow_filter_expression;
 mod record_batch;
 pub mod sql;
 pub mod store;