IsNormalizing( lst, mat )
returns true or  false according to whether  the matrix  mat leaves the
vectors in lst as a set invariant, i.e., Set(l * M) = Set( l ).
    gap> a := [ [ 1, 2 ], [ 3, 1 ] ];;
    gap> l := [ [ 1, 0 ], [ 0, 1 ], [ 1, 1 ], [ 0, 0 ] ];;
    gap> l * a;
    [ [ 1, 2 ], [ 3, 1 ], [ 4, 3 ], [ 0, 0 ] ]
    gap> IsNormalizing( l, a );
    false 
GAP 3.4.4