class_docstr: Preprocessor to convert notebooks to Python source to strips out all
  magics. To be applied after the preprocessors that can handle
  holoviews magics appropriately.
code: def __call__(self, nb, resources):
      return self.preprocess(nb, resources)
  
imports: import ast
  from nbconvert.preprocessors import Preprocessor
label_desc: Use image node_id 2 for calling the StripMagicsProcessor obj's underlying member method code with example usage: obj.__call__(nb, resources) and returns: self