Cant edit override pointer property.

Hi i create a pointer property with python in a bone, but when i override the collection, i can't edit this property, i try to put

is_overridiable=True but return this error:

'is_overridable' is an invalid keyword argument for PointerProperty()

Does anyone know if there is any way that it can be made overridable or not yet?

Thank youuuuuuuu