private void checkCollectionNullityOnAssignment(@NotNull PsiElement errorElement,
                                                      @Nullable PsiType expectedType,
                                                      @Nullable PsiType assignedType) {
        if (isNullableNotNullCollectionConflict(expectedType, assignedType, file, new HashSet<>())) {
          reportProblem(holder, errorElement, "assigning.a.collection.of.nullable.elements");
        }
      }
private void checkCollectionNullityOnAssignment(@NotNull PsiElement errorElement,
                                                      @Nullable PsiType expectedType,
                                                      @Nullable PsiType assignedType)