code: def rms_contrast(batch: List[np.array]) -> List[float]:
      """Return RMS contrast of image."""
      return [
          img.std() if _is_grayscale(img) else rgb2gray(img).std()
          for img in batch
      ]
  
imports: from typing import Dict, List, Tuple
  import numpy
  from cv2 import CV_64F, Laplacian
  from skimage.color import rgb2gray
label_desc: Use image node_id 4 for calling a global function with example usage: rms_contrast(batch) and returns: unknown