code: def forward(self, x):
      x = self.conv_bn_relu_1(x)
      x = self.conv_bn_relu_2(x)
      x = self.conv_bn_relu_3(x)
      return x
  
imports: from collections import OrderedDict
  from typing import List, Union
  import torch
  from torch import nn
  from pytorch_toolbelt.modules import ACT_RELU, instantiate_activation_block, ChannelSpatialGate2d
  from pytorch_toolbelt.modules.encoders import EncoderModule, make_n_channel_input
label_desc: Use image node_id 2 for calling the StemBlock obj's underlying member method code with example usage: obj.forward(x) and returns: x