Is there good documentation about what this means:

```
SomeType{T} where T:>SomeOtherType
```

and more generally:

```
SomeType{T} where SomeOtherType<:T<:YetAnotherype
```

I get this strange? result:

```
julia> Vector{Number}<:Vector{T} where String<:T<:Number
true
```

but String is not a subtype of Number.

and I would expect this type to be the empty set.

Thank you,