def GetMinMaxValues(self):
    MinPoint = lambda data: min(x for x in data if x is not None)
    MaxPoint = lambda data: max(x for x in data if x is not None)
    mins  = [MinPoint(series.data) for series in self.data if series.data]
    maxes = [MaxPoint(series.data) for series in self.data if series.data]
    if not mins or not maxes:
      return None, None # No data, just bail.
    return min(mins), max(maxes)
Get the largest & smallest values in this chart, returned as
dataset/ETHPy150Open AppScale/appscale/AppServer/google/appengine/_internal/graphy/common.py/BaseChart.GetMinMaxValues