class_docstr: SlowFast networks (SlowFast) from
  `"SlowFast Networks for Video Recognition"
  <https://arxiv.org/abs/1812.03982>`_ paper.
code: def forward(self, x):
      fast_input = x
      slow_input = x[:, :, :: self.slow_temporal_stride // 2, :, :]
  
      fast, lateral = self.FastPath(fast_input)
      slow = self.SlowPath(slow_input, lateral)
      x = torch.cat((slow, fast), dim=1)  # bx2304
  
      if self.feat_ext:
          return x
  
      x = self.dp(x)
      x = self.fc(x)  # bxnum_classes
      return x
  
imports: import torch
  import torch.nn
  from torch.nn import BatchNorm3d
label_desc: Use image node_id 2 for calling the SlowFast obj's underlying member method code with example usage: obj.forward(x) and returns: x, x