Identify all implicit and explicit instructions in this prompt:
I want this function to return none if the lengths of a and b are the same, but it does not do that. def longer(a: str, b: str): return a if len(a) > len(b) else b
a) Explicit: Return none if the lengths of a and b are the same.
b) Implicit: The function should compare the lengths of a and b.
c) Implicit: The function should return a if len(a) > len(b) else b.
d) Explicit: The function does not currently meet the desired condition.