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

def get_target_errors(self):
    """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


    """
    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