class_docstr: Slowfast for ACAR-Net.
  
  Args:
      - block (`Bottleneck`):
          Bottleneck module.
      - layers (`tuple or list`):
          Number of layers at different stages.
      - alpha (`int`):
          The frame rate ratio between the Fast and Slow pathway.
      - beta (`float`):
          The ratio of channels of the Slow pathway.
      - fuse_only_conv (`bool`):
          Whether to use conv only to fuse pathways.
      - fuse_kernel_size (`int`):
          Kernel size used to fuse pathways.
      - slow_full_span (`bool`):
          Whether to span inputs for Slow pathway.
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code: def fast_path(self, input):  # pylint: disable=W0622
      x = self.fast_conv1(input)
      x = self.fast_bn1(x)
      x = self.fast_relu(x)
      x = self.fast_maxpool(x)
      tc1 = self.t_conv1(x)
      x = self.fast_res1(x)
      tc2 = self.t_conv2(x)
      x = self.fast_res2(x)
      tc3 = self.t_conv3(x)
      x = self.fast_res3(x)
      tc4 = self.t_conv4(x)
      x = self.fast_res4(x)
      return x, [tc1, tc2, tc3, tc4]
  
file_path: towhee/towhee/models/acar_net/backbone.py
imports: import torch
  from torch import nn
label_desc: Use image node_id 4 for calling the SlowFast obj's underlying member method code with example usage: obj.fast_path(input) and returns: x,  list