import torch
from omnibias.torch import get_activation

x = torch.linspace(-2, 2, 9, dtype=torch.float64)
spec = get_activation("tanh")
first = spec.fastpath(x, 1)
expected = 1 - torch.tanh(x).square()

torch.testing.assert_close(first, expected)
print(first.shape)  # torch.Size([9])