Hi,
What you wrote is an old style function.
The equivalent new style would be:
class F_new(torch.autograd.Function):
    @staticmethod
    def forward(ctx, args, gamma):
        ctx.gamma = gamma
        pass

    @staticmethod
    def backward(ctx, args):
        pass

# Using your old style Function from your code sample:
F(gamma)(inp)
# Using the new style Function:
F_new.apply(inp, gamma)