dag.py : ind_nodes implementation has wrong code!!!

[aqibsaeed]

dag.py : ind_nodes implementation has wrong code!!!

[aqibsaeed]

Please submit a pull request with test cases.

[mrchaos]

example)
dag.graph : OrderedDict([('s1_1', {'s1_3'}), ('s1_2', {'s1_3'}), ('s1_3', set())])

1. dependent_nodes = set(tuple(node) for dependents in graph.items() for node in dependents)
   ==> {(), ('s', '1', '', '1'), ('s', '1', '', '2'), ('s', '1', '_', '3'), ('s1_3',)}

2. dependent_nodes = set(node for dependents in iter(graph.values() )for node in dependents)
   ==> {'s1_3'}

[aqibsaeed]

Currently I am busy, I will look into this later to understand/verify the issue.