Freeze the slice container pyclass as it does not need mutable access (or any access at all).

Author: adamreichold

src/slice_container.rs

@@ -4,7 +4,7 @@ use ndarray::{ArrayBase, Dimension, OwnedRepr};
 use pyo3::pyclass;
 
 /// Utility type to safely store `Box<[_]>` or `Vec<_>` on the Python heap
-#[pyclass]
+#[pyclass(frozen)]
 pub(crate) struct PySliceContainer {
     pub(crate) ptr: *mut u8,
     pub(crate) len: usize,