code: public void update(Instance ins) throws Exception {
      if(m_Instances==null)
        throw new Exception("No instances supplied yet. Cannot update without"+
                            "supplying a set of instances first.");
      m_DistanceFunction.update(ins);
    }
docs: Updates the LinearNNSearch to cater for the new added instance. This
  implementation only updates the ranges of the DistanceFunction class,
  since our set of instances is passed by reference and should already have
  the newly added instance.
  
  @param ins 	The instance to add. Usually this is the instance that
  is added to our neighbourhood i.e. the training
  instances.
  @throws Exception	if the given instances are null