code: def __init__(self, window_size=11, size_average=True):
      super(SSIM, self).__init__()
      self.window_size = window_size
      self.size_average = size_average
      self.channel = 1
      self.window = self.create_window(window_size, self.channel)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import math
  import paddle
  import paddle.nn
  import paddle.nn.functional
  from paddle import ParamAttr
  from ppdet.core.workspace import register
  from ppdet.modeling import ops
  from ppdet.modeling.losses.iou_loss import GIoULoss
  from ppdet.utils.logger import setup_logger
label_desc: Use image node_id 1 to create a new SSIM object from inherited base classes: nn with example: obj = SSIM(window_size, size_average)