Add generic support inside containers for calls to Python from Rust.

[iduartgomez]

While a bit unorthodox maybe should contemplate adding support for use of generic "PyObjects" to use inside container types (like python lists) when interfacing with python from Rust.

What is blocking this is the implementation of the typing module prevents usage of generics in things like the List type.

One solution would be to add an own (lightweight) implementation of a List type like it was done with Tuple (was impossible to check the contained types of Tuple using the typing module implementation).