structural entropy calculation

[Mutual-Luo]

i think there is something wrong in code
"""
def CombineDelta(node1, node2, cut_v, g_vol):
v1 = node1.vol + 1
v2 = node2.vol + 1
g1 = node1.g + 1
g2 = node2.g + 1
v12 = v1 + v2
return ((v1 - g1) * math.log2(v12 / v1) + (v2 - g2) * math.log2(v12 / v2) -
2 * cut_v * math.log2(g_vol / v12)) / g_vol
"""

I think it should return """ 2 * cut_v * math.log2(g_12 / vol) / g_vol """

if there is something that I misundersand, can you supply a further information of the calculation?

thank you very much