docstr: Parameters
  ----------
  mat : square matrix
      The matrix to be penalized.
  mat_inv : square matrix
      The inverse of `mat`.
  
  Returns
  -------
  A scalar penalty value
docstr_tok: ["Parameters","--","--","--","--","--","mat",":","square","matrix","The","matrix","to","be","penalized",".","mat_inv",":","square","matrix","The","inverse","of","`","mat","`",".","Returns","--","--","--","-","A","scalar","penalty","value"]
code: def func(self, mat, mat_inv):
      """
      Parameters
      ----------
      mat : square matrix
          The matrix to be penalized.
      mat_inv : square matrix
          The inverse of `mat`.
  
      Returns
      -------
      A scalar penalty value
      """
      raise NotImplementedError
  
imports: import numpy
label_desc: Use image node_id 2 for calling the CovariancePenalty obj's underlying member method code with example usage: obj.func(mat, mat_inv) without return types