Tuple's `process` and `process_encode` are not symmetrical

[valentunn]

Hey, I am facing an issue when working with the type of the following structure:

def: {
                Composite: {
                  fields: [
                    {
                      name: null
                      type: 357
                      typeName: Vec<Asset>
                      docs: []
                    }
                  ]
                }
              }

The library interpets it as a 1-dimensonal Tuple. Tuple usually correponds to the [T]/(T) python objects but 1-dimensonal tuple performs this unwrapping during process which results in decoded value to be just T. On the other side, process_encode there is no such check which results in error when you try to pass instances received from decode to encode which becomes tough when working with dry_run apis when you need to pass complex structures back and worth