class_docstr: Convert RGB or BGR image to grayscale. 
class_docstr_tok: ["Convert","RGB","or","BGR","image","to","grayscale","."]
code: def _augment(self, img, _):
      ret = super()._augment(img, _)
      if self.keepshape:
          return np.concatenate([ret] * 3, axis=2)
      else:
          return ret
  
file_path: tensorpack/tensorpack/dataflow/imgaug/convert.py
imports: import numpy
  import cv2
  from .base import PhotometricAugmentor
label_desc: Use image node_id 2 for calling the Grayscale obj's underlying member method code with example usage: obj._augment(img, _) and returns: np, ret