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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 _select_channels(data, channels):
 """Select channels. Parameters data : instance of ChanTime data with all the channels channels : list channels of interest Returns ------- instance of ChanTime data with only channels of interest Notes ----- This function does the same as wonambi.trans.select, but it's much faster. wonambi.trans.Select needs to flexible for any data type, here we assume that we have one trial, and that channel is the first dimension. """

    output = data._copy()
    chan_list = list(data.axis['chan'][0])
    idx_chan = [chan_list.index(i_chan) for i_chan in channels]
    output.data[0] = data.data[0][idx_chan, :]
    output.axis['chan'][0] = asarray(channels)

    return output