code: def _select_channels(data, channels):
      
      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
docs: 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.