What's wrong here?

What's wrong here? How do I make this work?

>>> from ezPyCrypto import key
>>> str = '4 big dogs.'
>>> key.encString(str)
Traceback (most recent call last):
  File "<pyshell#6>", line 1, in ?
    key.encString(str)
TypeError: unbound method encString() must be called with key instance as

first argument (got str instance instead)
>>> 

Thanks,
Nathan Pinno