<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def unserialize(cls, string):
 """Unserializes from a string. :param string: A string created by :meth:`serialize`. """

        id_s, created_s = string.split('_')
        return cls(int(id_s, 16),
                   datetime.utcfromtimestamp(int(created_s, 16)))