def _set_index_array(self):
    self.index_array = np.arange(self.n)
    if self.shuffle:
        self.index_array = np.random.permutation(self.n)
def _set_index_array(self):
    self.index_array = np.arange(self.n)
    if self.shuffle:
        self.index_array = np.random.permutation(self.n)