def METHOD_NAME(ppm: float, analyzer: AnalyzerType, at_mz=200):
    """
    Converts a ppm value at a given m/z to a sigma_1 value for use with MSIWarp.
    Effectively METASPACE and MSIWarp treat the two values the same way - as an m/z tolerance.
    However, ppm is proportional to a base m/z value (usually 200), whereas sigma_1 is an absolute
    value of Daltons measured at 1 Da.
    """
    if analyzer == 'orbitrap':
        return (at_mz * ppm / 1e6) / (at_mz ** 1.5)
    if analyzer == 'ft-icr':
        return (at_mz * ppm / 1e6) / (at_mz ** 2)
    return ppm / 1e6