docs: def all_successors(self, node, skip_reached_fixedpoint=False):
          """
          Returns all successors to the specific node.
  
          :param node: A node in the graph.
          :return:     A set of nodes that are all successors to the given node.
          :rtype:      set
          """
  
          successors = set()
  
          stack = [ node ]
          while stack:
              n = stack.pop()
              successors.add(n)
              stack.extend(succ for succ in self.successors(n) if
                           succ not in successors and
                              (not skip_reached_fixedpoint or succ not in self._reached_fixedpoint)
                           )
  
          return successors