code: def gelu(x):
    
    cdf = 0.5 * (1.0 + tf.tanh(
        (np.sqrt(2 / np.pi) * (x + 0.044715 * tf.pow(x, 3)))))
    return x * cdf
docs: Gaussian Error Linear Unit.
  
    This is a smoother version of the RELU.
    Original paper: https://arxiv.org/abs/1606.08415
  
    Args:
      x: float Tensor to perform activation.
  
    Returns:
      x with the GELU activation applied.