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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def time_until_expiration(self):
 """Returns the number of remaining days until user's password expires. Calculates the number days until the user must change their password, once the password expires the user will not able to log in until an admin changes its password. """

        if self.password_expires_at is not None:
            expiration_date = datetime.datetime.strptime(
                self.password_expires_at, "%Y-%m-%dT%H:%M:%S.%f")
            return expiration_date - datetime.datetime.now()