code: def get_target_errors(self):
      
      if self._target_errors: return self._target_errors
      v = []
      for i in range(len(self._target_hpas)):
        v.append(self.get_target_error(i))
      return v
docs: Just get a single error characterization based on the index relative to the target
  
      :param i: list index
      :type i: int
      :returns: list of base-wise errors
      :rtype: list of HPA groups