Returns True if some directed graph can realize the in- and out-degree sequences.
- in_sequence (list or iterable container) – A sequence of integer node in-degrees
- out_sequence (list or iterable container) – A sequence of integer node out-degrees
valid – True if in and out-sequences are digraphic False if not.
This algorithm is from Kleitman and Wang . The worst case runtime is O(s * log n) where s and n are the sum and length of the sequences respectively.
 D.J. Kleitman and D.L. Wang Algorithms for Constructing Graphs and Digraphs with Given Valences and Factors, Discrete Mathematics, 6(1), pp. 79-88 (1973)