code: func (m *metricVec) Delete(labels Labels) bool {
  	h, err := m.hashLabels(labels)
  	if err != nil {
  		return false
  	}
  
  	return m.metricMap.deleteByHashWithLabels(h, labels, m.curry)
  }
docs: // Delete deletes the metric where the variable labels are the same as those
  // passed in as labels. It returns true if a metric was deleted.
  //
  // It is not an error if the number and names of the Labels are inconsistent
  // with those of the VariableLabels in Desc. However, such inconsistent Labels
  // can never match an actual metric, so the method will always return false in
  // that case.
  //
  // This method is used for the same purpose as DeleteLabelValues(...string). See
  // there for pros and cons of the two methods.