@Nullable
  private PsiAnnotation createContractAnnotation(List<? extends MethodContract> contracts, MutationSignature signature) {
    return createContractAnnotation(myProject, signature.isPure(),
                                    StreamEx.of(contracts).select(StandardMethodContract.class).joining("; "),
                                    signature.isPure() || signature == MutationSignature.unknown() ? "" : signature.toString());
  }
@Nullable
  private PsiAnnotation createContractAnnotation(List<? extends MethodContract> contracts, MutationSignature signature)