MultirationalMap * MultirationalMap -- composition of multi-rational maps

i1 : ZZ/65521[x_0..x_4];

i2 : Psi = last graph rationalMap(projectiveVariety ideal(x_4,x_2^2-x_1*x_3,x_1*x_2-x_0*x_3,x_1^2-x_0*x_2),Dominant=>true);

o2 : MultirationalMap (dominant rational map from 4-dimensional subvariety of PP^4 x PP^7 to 4-dimensional subvariety of PP^7)

i3 : Phi = first graph Psi;

o3 : MultirationalMap (birational map from 4-dimensional subvariety of PP^4 x PP^7 x PP^7 to 4-dimensional subvariety of PP^4 x PP^7)

i4 : Eta = Phi * Psi;

o4 : MultirationalMap (dominant rational map from 4-dimensional subvariety of PP^4 x PP^7 x PP^7 to 4-dimensional subvariety of PP^7)

i5 : assert(Eta == last graph Psi);