Union with None / NoneType type does not behave as expected

I have a function with this signature:

```
def get_value(self)-> Union[NoneType, bool, i32, i64, float, str]:

```

Sometime this function returns None

When this happens, printing a returned value results in this :

```
ValueError: optional unpack failed: expected Union[Int[32] | Int[64] | NoneType | bool | float | str], got None

Raised from: std.internal.types.optional.unwrap.0:0
/Users/yfinkelstein/.codon/lib/codon/stdlib/internal/types/optional.codon:99:5

```

Is there a better way to model a return type that has a nuber of type alternatives or None ?

Also, another strange behavior:
if the function does not return anything ( a branch that does not have a return statement and just exits), the returned value has the type of the first template type in the Union after sorting by type name