How do you get the mean and std values of isic18

[FeliksFrancis]

How do you get the mean and std values here？
def init(self, data_name, train=True):
if data_name == 'isic18':
if train:
self.mean = 157.561
self.std = 26.706
else:
self.mean = 149.034
self.std = 32.022