AllMultiplicityFreeSelfPairedSubgroups

AllMultiplicityFreeSelfPairedSubgroups(G) returns the set of representatives of all conjugacy classes of proper subgroups H such that the Schurian scheme defined by G and H is symmetric. For example, we have the following result :

gap> AllMultiplicityFreeSelfPairedSubgroups(SpecialLinearGroup(2,4));
[ Group([ [ [ Z(2^2)^2, 0*Z(2) ], [ 0*Z(2), Z(2^2) ] ], 
      [ [ 0*Z(2), Z(2)^0 ], [ Z(2)^0, 0*Z(2) ] ] ]), 
  Group([ [ [ Z(2^2), Z(2)^0 ], [ Z(2)^0, 0*Z(2) ] ], 
      [ [ Z(2)^0, Z(2^2) ], [ 0*Z(2), Z(2)^0 ] ] ]), 
  Group([ [ [ Z(2)^0, Z(2)^0 ], [ 0*Z(2), Z(2)^0 ] ], 
      [ [ Z(2)^0, Z(2^2) ], [ 0*Z(2), Z(2)^0 ] ], 
      [ [ Z(2^2)^2, 0*Z(2) ], [ 0*Z(2), Z(2^2) ] ] ]), 
  Group([ [ [ Z(2^2), Z(2)^0 ], [ Z(2)^0, 0*Z(2) ] ] ]) ]