Maple cheat sheet

allvalues(pdsolve(4*H(u, u1)*(diff(H(u, u1), u1))+4*(diff(H(u, u1), u))*u1-u1)); simplify(allvalues(eval(%, _F1 = ((x)->x) ) ) )

another example

Sol := pdsolve(LieDerivative(L2, F(x, u[], u[1], u[1, 1]))); 
inv11 := eval(rhs(Sol), _F1 = ((x, y)-> x))
DGinfo(G, "CoefficientSet")
simplify(a*y+x, {-a*y+x = 0})
coeffs(4*x*y^5+x^2+x*y+y, [x, y], 't')

in t the terms are saved

base2formas := GenerateForms([baseformas], [2])
DGinfo("FrameNames")
allvalues()