added essential dependency test for Rhodes example (Krebs Cycle)

tst/lowerbound.tst

@@ -4,11 +4,17 @@ gap> LoadPackage("sgpdec", false);;
 gap> SgpDecFiniteSetDisplayOn();;
 gap> S := FullTransformationSemigroup(4);;
 gap> sk := Skeleton(S);;
-gap> CheckEssentialDependency(sk, 1,2);
-Group([ (2,3), (1,2), (1,3) ])
-gap> CheckEssentialDependency(sk, 2,3);
-Group([ (1,2) ])
-gap> SgpDecFiniteSetDisplayOff();;
-
-#
+gap> StructureDescription(CheckEssentialDependency(sk, 1,2));
+"S3"
+gap> StructureDescription(CheckEssentialDependency(sk, 2,3));
+"C2"
+gap> #Krebs Cycle Example from Rhodes (2010) Figure 3 Part I:
+gap> alpha:=   Transformation([2,2,4,4,5,2]);;  #NAD
+gap> beta:=     Transformation([1,3,3,4,5,6]);;  #NADP
+gap> gamma:=Transformation([1,2,3,5,5,6]);;  #GDP
+gap> delta:=    Transformation([1,2,3,4,6,6]);;  #NADP
+gap> KrebsK2:=Semigroup(alpha,beta, gamma,delta);;;
+gap> skel:=Skeleton(KrebsK2);;
+gap> StructureDescription(CheckEssentialDependency(skel,5,6));
+"C2"
 gap> STOP_TEST( "Sgpdec package: lowerbound.tst", 10000);