def METHOD_NAME(model, param, backwards):
    """Convert an MJD from TCB to TDB or vice versa.
        t_tdb = (t_tcb - IFTE_MJD0) / IFTE_K + IFTE_MJD0
        t_tcb = (t_tdb - IFTE_MJD0) * IFTE_K + IFTE_MJD0
    Parameters
    ----------
    model : pint.models.timing_model.TimingModel
        The timing model
    param : str
        The parameter name to be converted
    backwards : bool
        Whether to do TDB to TCB conversion.
    """
    factor = IFTE_K if backwards else 1 / IFTE_K
    tref = IFTE_MJD0
    if hasattr(model, param) and getattr(model, param).quantity is not None:
        par = getattr(model, param)
        assert isinstance(par, MJDParameter)
        par.value = (par.value - tref) * factor + tref
        if par.uncertainty_value is not None:
            par.uncertainty_value *= factor