Invalid positonal args cannot be passed over as kwargs using **kwargs

Input:
def a(x, y=None):
   print x, y

def b(x, **kw):
    a(x, **kw)

def c(x, y):
    print x, y

c(1, y=1)
b(1, y=2)
b(1, 3)

Output:
1 1
1 2
Traceback (most recent call last):
  File "a.py", line 12, in <module>
    b(1, 3)
TypeError: b() takes exactly 1 argument (2 given)

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