code: def insert(self, key, obj, future_expiration_minutes=15):
          
          expiration_time = self._calculate_expiration(future_expiration_minutes)
          self._CACHE[key] = (expiration_time, obj)
          return True
docs: Insert item into cache.
  
          :param key: key to look up in cache.
          :type key: ``object``
  
          :param obj: item to store in cache.
          :type obj: varies
  
          :param future_expiration_minutes: number of minutes item is valid
          :type param: ``int``
  
          :returns: True
          :rtype: ``bool``