def get_old_suppressions(self):
        raise NotImplementedError
Add a new formatter to the chart (convenience method).
dataset/ETHPy150Open cloudtools/nymms/nymms/suppress/suppress.py/SuppressionManager.get_old_suppressions--crossover with--dataset/ETHPy150Open AppScale/appscale/AppServer/google/appengine/_internal/graphy/common.py/BaseChart.AddFormatter