def muon_filter(image, thr_low = 0, thr_up = 1.e10):
    """
    Tag muon with a double threshold on the image photoelectron size 
    Default values apply no tagging

    Paramenters
    ---------
    image:      `np.ndarray` number of photoelectrons in each pixel
    thr_low: `float` lower size threshold in photoelectrons
    thr_up: `float` upper size threshold in photoelectrons

    Returns
    ---------
    `bool` it determines whether a muon was tagged or not

    """
    return image.sum() > thr_low and image.sum() < thr_up