def _simple_chooser(queue, remaining):
    """Default contraction chooser that simply takes the minimum cost option."""
    cost, k1, k2, k12 = heapq.heappop(queue)
    if k1 not in remaining or k2 not in remaining:
        return None  # candidate is obsolete
    return cost, k1, k2, k12
Default contraction chooser that simply takes the minimum cost option.
opt_einsum/paths.py