def isnorth(bb1, bb2):
    """ Returns True if bb1 is north of bb2
        
        For obj1 to be north of obj2
            - The min Y of bb1 is greater than the max Y of bb2
    """
    
    bb1_min, _ = bb1
    _, bb2_max = bb2
    
    x1,y1,z1 = bb1_min
    x2,y2,z2 = bb2_max
    
    return y1 > y2