fix(python): Use strings to expose ClosedInterval in expr IR (#16369)

Author: wence-

py-polars/src/lazyframe/visitor/expr_nodes.rs

@@ -36,22 +36,13 @@ pub struct Literal {
     dtype: PyObject,
 }
 
-#[pyclass(name = "ClosedInterval")]
-#[derive(Copy, Clone)]
-pub enum PyClosedInterval {
-    Both,
-    Left,
-    Right,
-    None,
-}
-
 impl IntoPy<PyObject> for Wrap<ClosedInterval> {
     fn into_py(self, py: Python<'_>) -> PyObject {
         match self.0 {
-            ClosedInterval::Both => PyClosedInterval::Both,
-            ClosedInterval::Left => PyClosedInterval::Left,
-            ClosedInterval::Right => PyClosedInterval::Right,
-            ClosedInterval::None => PyClosedInterval::None,
+            ClosedInterval::Both => "both",
+            ClosedInterval::Left => "left",
+            ClosedInterval::Right => "right",
+            ClosedInterval::None => "none",
         }
         .into_py(py)
     }

py-polars/src/lib.rs

@@ -107,7 +107,6 @@ fn _expr_nodes(_py: Python, m: &Bound<PyModule>) -> PyResult<()> {
     m.add_class::<PyOperator>().unwrap();
     m.add_class::<PyStringFunction>().unwrap();
     m.add_class::<PyBooleanFunction>().unwrap();
-    m.add_class::<PyClosedInterval>().unwrap();
     // Options
     m.add_class::<PyWindowMapping>().unwrap();
     m.add_class::<PyRollingGroupOptions>().unwrap();