def exportValue(self, vf, value):
        m = StrStrHashMap(value)
        keysAndValues = []
        for i in m.keys():
            keysAndValues.append(i)
            keysAndValues.append(m[i])
def get_evolution_covariances(self):
        """!
        @return (list) Covariance matrix (or variance in case of one-dimensional data) of each cluster on each step of clustering.