def METHOD_NAME(w):
    u = w["disp"]
    p = w["press"]
    F = grad(u) + identity(u)
    J = det(F)
    Js = .5 * (lmbda + p + 2. * np.sqrt(lmbda * mu + .25 * (lmbda + p) ** 2)) / lmbda
    dJsdp = ((.25 * lmbda + .25 * p + .5 * np.sqrt(lmbda * mu + .25 * (lmbda + p) ** 2))
             / (lmbda * np.sqrt(lmbda * mu + .25 * (lmbda + p) ** 2)))
    return J - (Js + (p + mu / Js - lmbda * (Js - 1)) * dJsdp)