code: def preprocess(self, data_group):
      raise NotImplementedError
  
      if self.channels is None:
          pass
  
      input_data = data_group.preprocessed_case
      output_data = np.take(input_data, self.channels, axis=-1)
  
      data_group.preprocessed_case = output_data
      self.output_data = output_data
  
file_path: DeepNeuro/deepneuro/preprocessing/classes.py
imports: import os
  import numpy
  from deepneuro.preprocessing.preprocessor import Preprocessor
  from deepneuro.utilities.util import add_parameter
label_desc: Use image node_id 3 for calling the GetCentroid obj's underlying member method code with example usage: obj.preprocess(data_group) without return types