class_docstr: _EfficientKMeans is primarily used by palettization to perform a k-means operation. This class also has an in-house
  implementation of k-means, called ``kmeans_pp`` which runs entirely on GPU and is ~10x faster than sklearn's API.
code: def rmse_error(self, a, b):
      return _torch.sqrt(_torch.mean(_torch.square(a - b)))
  
file_path: coremltools/coremltools/optimize/torch/palettization/_efficient_kmeans.py
imports: import numpy
  import torch
  import torch.distributed
label_desc: Use image node_id 9 for calling the _EfficientKMeans obj's underlying member method code with example usage: obj.rmse_error(a, b) and returns: _torch