<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def make_key(observer):
 """Construct a unique, hashable, immutable key for an observer."""


        if hasattr(observer, "__self__"):
            inst = observer.__self__
            method_name = observer.__name__
            key = (id(inst), method_name)
        else:
            key = id(observer)
        return key