Parametric type with value of custom type as type parameter

General Usage
2

From the manual:

Both abstract and concrete types can be parameterized by other types. They can also be parameterized by symbols, by values of any type for which [isbits](https://docs.julialang.org/en/v1/base/base/#Base.isbits) returns true (essentially, things like numbers and bools that are stored like C types or structs with no pointers to other objects), and also by tuples thereof.

It works:

julia> isbits(MyType(3))
true

julia> MyParametricType(MyType(3))
MyParametricType{MyType(3)}(MyType(3))