class_docstr: Abstract class for confusion matrix
  
  You shouldn't instantiate this class.
  You might instantiate ConfusionMatrix or BinaryConfusionMatrix classes
class_docstr_tok: ["Abstract","class","for","confusion","matrix","You","should","n't","instantiate","this","class",".","You","might","instantiate","ConfusionMatrix","or","BinaryConfusionMatrix","classes"]
docstr: Returns classes (method)
docstr_tok: ["Returns","classes","(","method",")"]
code: def _classes(self, df=None):
      """
      Returns classes (method)
      """
      if df is None:
          df = self.to_dataframe()
      idx_classes = (df.columns | df.index).copy()
      idx_classes.name = "Classes"
      return idx_classes
  
imports: import numpy
  import pandas
  import collections
  import pandas_ml
  from pandas_ml.confusion_matrix.stats import binom_interval, class_agreement, prop_test
label_desc: Use image node_id 6 for calling the ConfusionMatrixAbstract obj's underlying member method code with example usage: obj._classes(df) and returns: idx_classes