test.py

## first use case
inp = torch.randn(3, 3)

a = torch.jit.script(F.dropout)
a(inp)

## error:
# RuntimeError: 

# undefined value _VF:
# at /scratch/wanchaol/local/pytorch/torch/nn/functional.py:800:13

# second use case

class Test(nn.Module):
    def __init__(self):
        super(Test, self).__init__()

    def forward(self, input):
        return F.dropout(input)

b = torch.jit.script(Test())
b(inp)

## works well