i1 :  A general cubic fourfold of discriminant 26
X = specialCubicFourfold("3nodal septic scroll",ZZ/33331);
o1 : ProjectiveVariety, cubic fourfold containing a surface of degree 7 and sectional genus 0

i2 : describe X
o2 = Special cubic fourfold of discriminant 26
containing a 3nodal surface of degree 7 and sectional genus 0
cut out by 13 hypersurfaces of degree 3

i3 : time f = detectCongruence(X,Verbose=>true);
number lines contained in the image of the cubic map and passing through a general point: 8
number 2secant lines = 7
number 5secant conics = 1
 used 10.3856 seconds
o3 : Congruence of 5secant conics to surface in PP^5

i4 : p := point ambient X  random point on P^5
o4 = point of coordinates [15092, 9738, 3620, 15181, 12688, 1]
o4 : ProjectiveVariety, a point in PP^5

i5 : time C = f p;  5secant conic to the surface
 used 1.00869 seconds
o5 : ProjectiveVariety, curve in PP^5

i6 : assert(dim C == 1 and degree C == 2 and dim(C * surface X) == 0 and degree(C * surface X) == 5 and isSubset(p, C))
