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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def load_rnn_checkpoint(cells, prefix, epoch):
 """Load model checkpoint from file. Pack weights after loading. Parameters cells : mxnet.rnn.RNNCell or list of RNNCells The RNN cells used by this symbol. prefix : str Prefix of model name. epoch : int Epoch number of model we would like to load. Returns ------- symbol : Symbol The symbol configuration of computation network. arg_params : dict of str to NDArray Model parameter, dict of name to NDArray of net's weights. aux_params : dict of str to NDArray Model parameter, dict of name to NDArray of net's auxiliary states. Notes ----- - symbol will be loaded from ``prefix-symbol.json``. - parameters will be loaded from ``prefix-epoch.params``. """

    sym, arg, aux = load_checkpoint(prefix, epoch)
    if isinstance(cells, BaseRNNCell):
        cells = [cells]
    for cell in cells:
        arg = cell.pack_weights(arg)

    return sym, arg, aux