code: def to_cache_timer(datetime_func):
      
      if datetime_func is None:
          datetime_func = datetime.utcnow
  
      def _timer():
          """Return the timestamp since the epoch."""
          return (datetime_func() - datetime(1970, 1, 1)).total_seconds()
  
      return _timer
docs: Converts a datetime_func to a timestamp_func.
  
      Args:
         datetime_func (callable[[datatime]]): a func that returns the current
           time
  
      Returns:
         time_func (callable[[timestamp]): a func that returns the timestamp
           from the epoch