@Override
  public void beforeValueReturn(@NotNull DfaValue value,
                                @Nullable PsiExpression expression,
                                @NotNull PsiElement context,
                                @NotNull DfaMemoryState state) {
    if (context instanceof PsiMethod || context instanceof PsiLambdaExpression) {
      myAlwaysReturnsNotNull = myAlwaysReturnsNotNull && !state.getDfType(value).isSuperType(DfTypes.NULL);
    }
  }
@Override
  public void beforeValueReturn(@NotNull DfaValue value,
                                @Nullable PsiExpression expression,
                                @NotNull PsiElement context,
                                @NotNull DfaMemoryState state)