code: def grp_list(items):
      
      grp = []
      res = []
      for item in items:
          if isinstance(item, urwid.Divider):
              res.append(grp)
              grp = [items[0]]
          else:
              grp.append(item)
      res.append(grp)
      return res[1:]
docs: Organize list of items [a,2,3,4,a,4,2,a,1, etc...] like:
          [[a,2,3,4], [a,4,2], [a,1]], where 'a' is a urwid.Divider