<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def create_with( cls, event: str = None, observable: T.Union[str, Observable] = None """Creates a partial application of ObservableProperty with event and observable preset."""


        return functools.partial(cls, event=event, observable=observable)