<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def pretty_timestamp(timestamp, date_format='%a-%m_%d_%y:%H:%M:%S'):
 """Huminize timestamp."""

    return time.strftime(date_format,
                         time.localtime(int(str(timestamp)[:10])))