Avoid initializing kwargs in signature as they might not work as expected when you need to pass kwargs from other methods

$ cat test_kwargs.py 
def m1(a, b=2):
    print a, b
def m2(a, b=None):
    ​m1(a, b=b)
m1(1)
m2(1)
m1(1, 2)
m2(1, 2)
$ python test_kwargs.py 
1 2
1 None
1 2
1 2
A better version of the above methods would be,​

$ cat test_kwargs.py 
def m1(a, b=None):
    if b is None:
        b = 2
    print a, b

def m2(a, b=None):
    m1(a, b=b)

m1(1)
m2(1)
m1(1, 2)
m2(1, 2)
$ python test_kwargs.py 
1 2
1 2
1 2
1 2​