torch.nn.functional.gelu
torch.nn.functional.gelu(input, approximate='none') -> Tensor
When the approximate argument is 'none', it applies element-wise
   the function \text{GELU}(x) = x * \Phi(x)
where \Phi(x) is the Cumulative Distribution Function for Gaussian
   Distribution.
When the approximate argument is 'tanh', Gelu is estimated with
  \text{GELU}(x) = 0.5 * x * (1 + \text{Tanh}(\sqrt(2 / \pi) * (x
  + 0.044715 * x^3)))

See Gaussian Error Linear Units (GELUs).