Returns True if some pseudograph can realize the sequence.
Every nonnegative integer sequence with an even sum is pseudographical (see ).
Parameters: sequence (list or iterable container) – A sequence of integer node degrees Returns: valid – True if the sequence is a pseudographic degree sequence and False if not. Return type: bool
The worst-case run time is \(O(n)\) where n is the length of the sequence.
 F. Boesch and F. Harary. “Line removal algorithms for graphs and their degree lists”, IEEE Trans. Circuits and Systems, CAS-23(12), pp. 778-782 (1976).