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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 eeg_select_channels(raw, channel_names):
 """ Select one or several channels by name and returns them in a dataframe. Parameters raw : mne.io.Raw Raw EEG data. channel_names : str or list Channel's name(s). Returns channels : pd.DataFrame Channel. Example Notes *Authors* - `Dominique Makowski <https://dominiquemakowski.github.io/>`_ *Dependencies* - mne *See Also* - mne package: http://martinos.org/mne/dev/index.html """

    if isinstance(channel_names, list) is False:
        channel_names = [channel_names]

    channels, time_index = raw.copy().pick_channels(channel_names)[:]
    if len(channel_names) > 1:
        channels = pd.DataFrame(channels.T, columns=channel_names)
    else:
        channels = pd.Series(channels[0])
        channels.name = channel_names[0]
    return(channels)