boundaries -- make the subalgebra of boundaries

i1 : L=lieAlgebra({a,b},Signs=>{1,0},Weights=>{{2,0},{2,1}},
         LastWeightHomological=>true,Field=>ZZ/3)

o1 = L

o1 : LieAlgebra

i2 : L=differentialLieAlgebra{0_L,a}

o2 = L

o2 : LieAlgebra

i3 : B=boundaries L

o3 = B

o3 : LieSubAlgebra

i4 : dims(10,B)

o4 = | 0 1 0 1 0 0 0 0 0 0 |
     | 0 0 0 0 0 0 0 1 0 1 |
     | 0 0 0 0 0 0 0 1 0 1 |
     | 0 0 0 0 0 0 0 0 0 1 |
     | 0 0 0 0 0 0 0 0 0 0 |
     | 0 0 0 0 0 0 0 0 0 0 |
     | 0 0 0 0 0 0 0 0 0 0 |
     | 0 0 0 0 0 0 0 0 0 0 |
     | 0 0 0 0 0 0 0 0 0 0 |
     | 0 0 0 0 0 0 0 0 0 0 |

              10        10
o4 : Matrix ZZ   <--- ZZ