def exclude_crds_mask_pix(bad_pix, existing_bad_pix):
    """Find differences between a set of newly-identified bad pixels
    and an existing set. Return a list of newly-discovered bad pixels
    that are not present in the existing set.

    Parameters
    ----------
    bad_pix : numpy.ndarray
        2D array of bad pixel flags. Flags must correspond to the
        defintiions used by the JWST calibration pipeline


    existing_bad_pix : numpy.ndarray
        2D array of bad pixel flags. Flags must correspond to the
        definitions used by the JWST calibration pipeline

    Returns
    -------
    new_bad_pix : numpy.ndarray
        2D array of bad pixel flags contained in ``bad_pix``
        but not ``existing_bad_pix``
    """
    return bad_pix - (bad_pix & existing_bad_pix)