code: private List<ScmMaterial> filterScmMaterials() {
          List<ScmMaterial> scmMaterials = new ArrayList<>();
          for (Material material : this) {
              if (material instanceof ScmMaterial) {
                  scmMaterials.add((ScmMaterial) material);
              }
          }
          return scmMaterials;
      }
docs: /*
  To two methods below are to avoid creating methods on already long Material interface with a No Op implementations.