docs: def get_path_fields(cls, base=[]):
      """Get object fields used for calculation of django-tutelary object
      paths.
  
      """
      pfs = []
      for pf in cls.TutelaryMeta.path_fields:
          if pf == 'pk':
              pfs.append(base + ['pk'])
          else:
              f = cls._meta.get_field(pf)
              if isinstance(f, models.ForeignKey):
                  pfs += get_path_fields(f.target_field.model, base=base + [pf])
              else:
                  pfs.append(base + [f.name])
      return pfs