guide: note __hash__ can have any integer type up to 64 bits

guide/src/class/protocols.md

@@ -44,7 +44,7 @@ given signatures should be interpreted as follows:
 
   - `__hash__(<self>) -> isize`
 
-    Objects that compare equal must have the same hash value.
+    Objects that compare equal must have the same hash value. Any type up to 64 bits may be returned instead of `isize`, PyO3 will convert to an isize automatically (wrapping unsigned types like `u64` and `usize`).
     <details>
     <summary>Disabling Python's default hash</summary>
     By default, all `#[pyclass]` types have a default hash implementation from Python. Types which should not be hashable can override this by setting `__hash__` to `None`. This is the same mechanism as for a pure-Python class. This is done like so: