This does not immediately reject the promise;
instead, an LSP $/cancelRequest notification is sent to the Lean server
The request handler can choose to ignore it,
to return a partial result,
or to produce a RequestCancelled error.
Does nothing if the promise has already been resolved or rejected.
Can be used to cancel the request.
This does not immediately reject the promise; instead, an LSP
$/cancelRequestnotification is sent to the Lean server The request handler can choose to ignore it, to return a partial result, or to produce aRequestCancellederror.Does nothing if the promise has already been resolved or rejected.