using dict for data attributes instead of self

[Alexander Kervero]

 Hi ,today i was reading diveinto python book,in chapter 5 it has a very
generic module to get file information,html,mp3s ,etc.

The code of the example is here : 
 http://diveintopython.org/object_oriented_framework/index.html 

One thing that i have some doubs is this part : 

 class FileInfo(UserDict):
    "store file metadata"
    def __init__(self, filename=None):
        UserDict.__init__(self)
        self["name"] = filename


So why does he wants a dictionary-like base class if he never uses any
dictionary method,except for dict.clear which is not necesary.

--
could be done like this?

  class FileInfo():
    "store file metadata"
    def __init__(self, filename=None):
        UserDict.__init__(self)
        self.name = filename

And the FileInfo subclasses could have the specific attributes that belongs
to each file type,for example mp3.

check the link to the full example. 
--

The only reason is to have a base class with arbitrary attributes ? so it
can dinamicaly adquire attributes depending of its subclass or something
like that?

Is there a clearer way to do it? Is there any benefits of going this way
that i dont see? 

Maybe this is just a dummy example to just show some functionality related
to the chapter? I am a bit confused.