[chaley]

I agree with user_none. You should be using a subclass. You wouldn't be the first. There are subclasses of Metadata in the device drivers.

You can avoid attribute/method collision by prefixing your methods and attributes with something, such as sb_.

Regarding getting instances from get_metadata, do something like:

class SeriesBook(Metadata):
  def __init__(self, title, author):
    Metadata.__init__(self, title, author)
    ....