def METHOD_NAME(src, band, fallback=None, override=None):
    """Figure out what value to use for nodata given a band and fallback/override
    settings
    :param src: Rasterio file
    """
    if override is not None:
        return override
    band0 = band if isinstance(band, int) else band[0]
    nodata = src.nodatavals[band0 - 1]
    if nodata is None:
        return fallback
    return nodata