def METHOD_NAME(rect):
    "Return the annular sector that circumscribes the given rectangle"
    if rect is None:
        return None
    x, y, dx, dy = rect
    points = [(x, y), (x, y+dy), (x+dx, y), (x+dx, y+dy)]
    radius2 = [x*x + y*y for x,y in points]
    if x <= 0 and x+dx >= 0 and y <= 0 and y+dy >= 0:
        return Box(0, -pi, sqrt(max(radius2)), 2*pi)
    else:
        angles = [atan2(y, x) for x,y in points]
        rmin, amin = sqrt(min(radius2)), min(angles)
        return Box(rmin, amin, sqrt(max(radius2)) - rmin, max(angles) - amin)