docs: def extract(self, obj, bypass_ref=False):
          """
          Extract parent of obj, according to current token.
  
          :param obj: the object source
          :param bypass_ref: not used
          """
          for i in range(0, self.stages):
              try:
                  obj = obj.parent_obj
              except AttributeError:
                  raise UnstagedError(obj, '{!r} must be staged before '
                                           'exploring its parents'.format(obj))
          if self.member:
              return obj.parent_member
          return obj