Understanding __deepcopy__

[carlos-jenkins]

In section "Copying":

http://www.rafekettler.com/magicmethods.html#copying

Says:

When you want to deep copy an individual attribute, call copy.deepcopy() on that attribute with memodict as the first argument.

Official documentation for Python 3 says:

https://docs.python.org/2/library/copy.html#copy.deepcopy

If the deepcopy() implementation needs to make a deep copy of a component, it should call the deepcopy() function with the component as first argument and the memo dictionary as second argument.

So:

1. It should be nice that the wording "first", "second", etc, match. It was a little bit confusing for me.
2. At least as the way I do understand it, memodict doesn't seem to work as documented:

>>> memodict = {}
>>> data = {'a': [1,2,3]}
>>> from copy import deepcopy
>>> deepcopy(data, memodict=memodict)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: deepcopy() got an unexpected keyword argument 'memodict'

Thanks.