class_docstr: Class for averaging note evaluations.
docstr: Mean of the errors.
docstr_tok: ["Mean","of","the","errors","."]
code: def mean_error(self):
      """Mean of the errors."""
      warnings.warn(
          "mean_error is given for all notes, this will change!"
      )
      return np.nanmean([e.mean_error for e in self.eval_objects])
  
imports: from __future__ import absolute_import, division, print_function
  import warnings
  import numpy
  from .None import evaluation_io, MultiClassEvaluation, SumEvaluation, MeanEvaluation
  from .onsets import onset_evaluation, OnsetEvaluation
  from ..io import load_notes
label_desc: Use image node_id 1 for calling the NoteMeanEvaluation obj's underlying member method code with example usage: obj.mean_error() and returns: np