class_docstr: Default preprocess block used by GluonCV.
  
  The default preprocess block includes:
  
      - mean [123.675, 116.28, 103.53]
  
      - std [58.395, 57.12, 57.375]
  
      - transpose to (B, 3, H, W)
  
  It is used to transform from resized original images with shape (1, H, W, 3) or (B, H, W, 3)
  in range (0, 255) and RGB color format.
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code: def hybrid_forward(self, F, x, init_mean, init_scale):
      x = F.broadcast_minus(x, init_mean)
      x = F.broadcast_div(x, init_scale)
      x = F.transpose(x, axes=(0, 3, 1, 2))
      return x
  
file_path: gluon-cv/gluoncv/utils/export_helper.py
imports: from __future__ import absolute_import
  import copy
  import mxnet
  from mxnet.base import MXNetError
  from mxnet.gluon import HybridBlock
  from mxnet.gluon import nn
label_desc: Use image node_id 2 for calling the _DefaultPreprocess obj's underlying member method code with example usage: obj.hybrid_forward(F, x, init_mean, init_scale) and returns: x