def form_pos_pair(info, i, mode='trn'):
    """
    Returns a list of 2 indices, i and another index j corresponding
    to a location in info which is of the same character as i.
    """
    y = info[info.Mode == mode]
    char = info.Char.loc[i]
    drawer = info.Drawer.loc[i]
    new_ind = y[(~y.Drawer.isin([drawer])) &
                y.Char.isin([char])].sample(1).index.values[0]
    return [i, new_ind]