def METHOD_NAME(mzs: Union[np.array, float], instrument: str, ppm: float):
    """Returns the expected half-width of a window that is +/- `ppm` ppm at BASE_MZ (200)
    and scales according to the peak-width scaling characteristics of the selected analyzer.
    """
    if instrument == 'TOF':
        return mzs * ppm * 1e-6
    elif instrument == 'Orbitrap':
        return mzs ** 1.5 * (ppm * 1e-6 / BASE_MZ ** 0.5)
    elif instrument == 'FTICR':
        # NOTE: In previous versions the FTICR scaling was incorrect, however it only affected
        # analysis_version==2
        return mzs ** 2 * (ppm * 1e-6 / BASE_MZ)
    else:
        raise ValueError(f'Unknown instrument: {instrument}')