Error with couchdb.mapping documents (load, store)

Howdy; just started using CouchDB-Python, but unfortunately I've
already run into an error. When I'm defining a mapping between a
couchdb document and a python object with class, load and store don't
work. I've confirmed (by looping through 'id in db') that I'm actually
connecting to the database and there's actually data there that the
library can read; this only fails with .mapping.

This is what my code looks like, seems pretty straightforward.

>>> from couchdb import Server, Document
>>> from couchdb.mapping import TextField
>>> server = Server()
>>> db = server['opettelukortit']
>>> class Sana(Document):
... suomi = TextField()
... englanti = TextField()
...
>>> s = Sana.load(db, 'da6bd85034c58b2ae1466f9af20016c6')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: type object 'Sana' has no attribute 'load'
>>>