Why should it be treated as follows function?

[luckhhn]

def preprocess_input(x, v2=True):

scale the raw pixel intensities to the range [0, 1]

x = x.astype('float32')
x = x / 255.0
if v2:
    x = x - 0.5
    x = x * 2.0
return x

Thank you very much for your work, Looking forward to your reply

[luckhhn]

What is the purpose of the above processing？