def gab_oris_shared_U(gab_letters, gab_oris):
    """
    gab_oris_shared_U(gab_letters, gab_oris)

    Returns Gabor orientations that are shared with U frames, for each gabor 
    letter, ordered together.

    Required args:
        - gab_letters (str): Gabor letters for which to retrieve orientations
        - gab_oris (list)  : Gabor orientations that can be included

    Returns:
        - new_oris (list): list of orientations for each Gabor letter
    """

    shared_oris = [90, 135] # from ABCD reference

    new_oris = []
    for lett in gab_letters:
        is_U = (lett.upper() == "U")
        if is_U and len(lett) > 1:
            raise NotImplementedError("Cannot return shared orientations if "
                "U Gabors are grouped with other Gabor letters.")
        oris = [ori - 90 * is_U for ori in shared_oris if ori in gab_oris]
        new_oris.append(oris) 

    return new_oris