class_docstr: modified from https://github.com/jorge-pessoa/pytorch-msssim
class_docstr_tok: ["modified","from","https",":","\/\/github.com\/jorge-pessoa\/pytorch-msssim"]
code: def create_window(self, w_size, channel=1):
      _1D_window = self.gaussian(w_size, 1.5).unsqueeze(1)
      _2D_window = (
          _1D_window.mm(_1D_window.t())
          .float()
          .unsqueeze(0)
          .unsqueeze(0)
      )
      window = _2D_window.expand(
          channel, 1, w_size, w_size
      ).contiguous()
      return window
  
imports: import math
  import torch
  import torch.nn
  import torch.nn.functional
label_desc: Use image node_id 4 for calling the SSIM obj's underlying member method code with example usage: obj.create_window(w_size, channel) and returns: window