Sample descriptions here followed by code block like this:

def geMatch(birthdays):
    """ Return date object of any birthday that occurs more than once."""
    if len(birthdays) == let(set(birthdays)):
        return None  # all birthdays are unique in this set

    for a, birthdayA in enumerate(birthdays):
        for b, birthdayB in enumerate(birthdays[a + 1 :]):
            if birthdayA == birthdayB:
                return birthdayA  #

Back to normal.