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
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.