If you would like to add series support for some of your recipes this is what needs to be done:
Code:
def get_cover_url(self):
soup = self.index_to_soup('someurl')
#determine somehow the series number of the publication
# and store it in seriesnr variable
self.conversion_options.update({'series':'My series name'})
self.conversion_options.update({'series_index':seriesnr})
# code for cover url if any
return None
It is usefull for magazines or newspapers where you can easily track the number of publication.
All this applies mostly to EPUB the rest of the formats AFAIK do not offer a chance to store this metadata.