class_docstr: Pytorch has a number of built-in activation functions.  We group those here under a common
  type, just to make it easier to configure and instantiate them `from_params` using
  `Registrable`.
  
  Note that we're only including element-wise activation functions in this list.  You really need
  to think about masking when you do a softmax or other similar activation function, so it
  requires a different API.
code: def forward(self, x: torch.Tensor) -> torch.Tensor:
      raise NotImplementedError
  
imports: import math
  import torch
  from allennlp.common import Registrable
label_desc: Use image node_id 1 for calling the Activation obj's underlying member method code with example usage: obj.forward(x) without return types