Extend WordList by appending elements from ``iterable``. If an element
    is a string, appends a :class:`Word <Word>` object.

def extend(self, iterable):
    """Extend WordList by appending elements from ``iterable``. If an element
    is a string, appends a :class:`Word <Word>` object.
    """
    [self._collection.append(Word(e) if isinstance(e, basestring) else e)
        for e in iterable]
    return self