title: UndefinedMetricWarning: No positive samples in y_true, true positive value should be meaningless UndefinedMetricWarning)
body: <p>I got this warning</p>
  
  <blockquote>
    <p>UndefinedMetricWarning: No positive samples in y_true, true positive
    value should be meaningless  UndefinedMetricWarning)</p>
  </blockquote>
  
  <p>Do you have any idea what it means?</p>