class_docstr: Simple stem for ImageNet: 3x3, BN, AF.
class_docstr_tok: ["Simple","stem","for","ImageNet",":","3x3",",","BN",",","AF","."]
code: def __init__(self, w_in, w_out, norm, activation_class):
      super().__init__(w_in, w_out, 2)
      self.conv = conv2d(w_in, w_out, 3, stride=2)
      self.bn = get_norm(norm, w_out)
      self.af = activation_class()
  
imports: import numpy
  from torch import nn
  from detectron2.layers import CNNBlockBase, ShapeSpec, get_norm
  from .backbone import Backbone
label_desc: Use image node_id 1 to create a new SimpleStem object from inherited base classes: CNNBlockBase with example: obj = SimpleStem(w_in, w_out, norm, activation_class)