code: protected IConceptSet getB(int A, int r) {
          if (A >= CONCEPTS) {
              resizeConcepts(A);
          }
          if (r >= ROLES) {
              resizeRoles(r);
          }
          final int index = indexOf(A, r);
          if (null == data[index]) {
              data[index] = new SparseConceptSet();
              addRole(r);
  
              if (null != base && index < base.length && null != base[index]) {
                  data[index].addAll(base[index]);
              }
          }
          return data[index];
      }
docs: Returns {B | A [ r.B} or {B | (A,B) in R(r)}
  
  @param A
  @param r
  @return