code: def sort(self, func=None):
  		
   		if func:
  			self.data.sort(func)
  		else:
  			self.data.sort()
docs: Sorts 'self.data' in-place. Argument:
  		- func : optional, default 'None' --
  			- If 'func' not given, sorting will be in ascending
  			  order.
  			- If 'func' given, it will determine the sort order.
  			  'func' must be a two-argument comparison function
  			  which returns -1, 0, or 1, to mean before, same,
  			  or after ordering.