def exportValue(self, vf, value):
        m = StrStrHashMap(value)
        keysAndValues = []
        for i in m.keys():
            keysAndValues.append(i)
            keysAndValues.append(m[i])
def pre_drop(self):
        """
        This is a routine which you could override to backup the tenant schema before dropping.
        :return:
        """