code: def true_positives(self, idx):
      return self.cm[idx, idx]
  
imports: import logging
  from collections import OrderedDict
  import numpy
  from sklearn import metrics
  from sklearn.metrics import confusion_matrix
label_desc: Use image node_id 3 for calling the ConfusionMatrix obj's underlying member method code with example usage: obj.true_positives(idx) and returns: self