(graph, get_edges)
return ordered_nodes
Topologically sort based on a user provided edge definition.

  Args:
    graph: A list of node names.
    get_edges: A function mapping from node name to a hashable collection
               of node names which this node has outgoing edges to.
  Returns:
    A list containing all of the node in graph in topological order.
    It is assumed that calling get_edges once for each node and caching is
    cheaper than repeatedly calling get_edges.
  Raises:
    CycleError in the event of a cycle.
  Example:
    graph = {'a': '$(b) $(c)', 'b': 'hi', 'c': '$(b)'}
    def GetEdges(node):
      return re.findall(r'\$\(([^))]\)', graph[node])
    print TopologicallySorted(graph.keys(), GetEdges)
    ==>
    ['a', 'c', b']
Topologically sort based on a user provided edge definition.
Topologically sort based on a user provided edge definition .
def TopologicallySorted(graph, get_edges):
  """Topologically sort based on a user provided edge definition.

  Args:
    graph: A list of node names.
    get_edges: A function mapping from node name to a hashable collection
               of node names which this node has outgoing edges to.
  Returns:
    A list containing all of the node in graph in topological order.
    It is assumed that calling get_edges once for each node and caching is
    cheaper than repeatedly calling get_edges.
  Raises:
    CycleError in the event of a cycle.
  Example:
    graph = {'a': '$(b) $(c)', 'b': 'hi', 'c': '$(b)'}
    def GetEdges(node):
      return re.findall(r'\$\(([^))]\)', graph[node])
    print TopologicallySorted(graph.keys(), GetEdges)
    ==>
    ['a', 'c', b']
  """
  get_edges = memoize(get_edges)
  visited = set()
  visiting = set()
  ordered_nodes = []
  def Visit(node):
    if node in visiting:
      raise CycleError(visiting)
    if node in visited:
      return
    visited.add(node)
    visiting.add(node)
    for neighbor in get_edges(node):
      Visit(neighbor)
    visiting.remove(node)
    ordered_nodes.insert(0, node)
  for node in sorted(graph):
    Visit(node)
  return ordered_nodes
def TopologicallySorted ( graph , get_edges ) : get_edges = memoize ( get_edges ) visited = set ( ) visiting = set ( ) ordered_nodes = [ ] def Visit ( node ) : if node in visiting : raise CycleError ( visiting ) if node in visited : return visited . add ( node ) visiting . add ( node ) for neighbor in get_edges ( node ) : Visit ( neighbor ) visiting . remove ( node ) ordered_nodes . insert ( 0 , node ) for node in sorted ( graph ) : Visit ( node ) return ordered_nodes