code: def get_crumbs(self):
          
          crumbs = []
          for cls in reversed(type(self).__mro__[1:]):
              crumbs.extend(getattr(cls, 'crumbs', ()))
          crumbs.extend(list(self.crumbs))
          return tuple(crumbs)
docs: Get crumbs for navigation links.
  
          Returns:
              tuple:
                  concatenated list of crumbs using these crumbs and the
                  crumbs of the parent classes through ``__mro__``.