error[E0277]: `Rc<i32>` cannot be sent between threads safely
 --> tests/ui/pyclass_send.rs:4:1
  |
4 | #[pyclass]
  | ^^^^^^^^^^ `Rc<i32>` cannot be sent between threads safely
  |
  = help: within `NotThreadSafe`, the trait `Send` is not implemented for `Rc<i32>`
note: required because it appears within the type `NotThreadSafe`
 --> tests/ui/pyclass_send.rs:5:8
  |
5 | struct NotThreadSafe {
  |        ^^^^^^^^^^^^^
note: required by a bound in `SendablePyClass`
 --> src/impl_/pyclass.rs
  |
  | pub struct SendablePyClass<T: Send>(PhantomData<T>);
  |                               ^^^^ required by this bound in `SendablePyClass`
  = note: this error originates in the attribute macro `pyclass` (in Nightly builds, run with -Z macro-backtrace for more info)