def save_tof_instrument(obj, filename, filetype='ascii', overwrite=True):
    """Saves a TOF instrument configuration into files for loading with
    :py:func:`.load_instrument`.

    Parameters
    ----------
    obj : object
        Instrument object

    filename : str
        Path to file (extension determined by filetype parameter).

    filetype : str, optional
        Default: `'ascii'`. Support for `'ascii'`, `'hdf5'`, or `'taz'`.

    overwrite : bool, optional
        Default: False. If True, overwrites the file, otherwise appends or
        creates new files.

    """
    instr_attrs = []
    if filetype == 'ascii':
        pass
    elif filetype == 'hdf5':
        pass
    elif filetype == 'taz':
        keys = {'viol_dist_pulse_mono': ['', 1000], 'viol_dist_mono_sample':
            ['', 100], 'viol_dist_sample_det': ['', 500],
            'viol_dist_pulse_mono_sig': ['', 1],
            'viol_dist_mono_sample_sig': ['', 1],
            'viol_dist_sample_det_sig': ['', 1], 'viol_angle_ph_f': ['', 0],
            'viol_angle_ph_f_sig': ['', 0.4], 'viol_angle_ph_i': ['', 0],
            'viol_angle_ph_i_sig': ['', 0.4], 'viol_angle_tt_f_sig': ['', 
            0.4], 'viol_angle_tt_i': ['', 0], 'viol_angle_tt_i_sig': ['', 
            0.4], 'viol_time_det_sig': ['', 5], 'viol_time_mono_sig': ['', 
            5], 'viol_time_pulse_sig': ['', 50], 'viol_det_sph': ['', 1]}
    else:
        raise ValueError(
            "Format not supported. Please use 'ascii', 'hdf5', or 'taz'")
