Function and method return types

[toaction]

Currently, all function/method return types are *py.Object, rather than concrete Python types.

In actual usage, we may need to convert *py.Object to concrete Python types in order to use type-specific features, such as calling methods within a class.

For example, if a function actually returns a class object. Current approach:

type Animal struct {
    py.Object
}

// return Animal obj
func Example() *py.Object

Expected:

type Animal struct {
    py.Object
}

func Example() *Animal

This way, methods within the Animal class can be called directly.