Cannot use interface methods when returned through function returning `[]Interface` type

[Jackenmen]

Reproduction steps:

1. Run commands:

mkdir dum
cd dum
go mod init dummy.com/dum
mkdir hello

2. Create file named hello/hello.go with following contents:

package hello

type Example interface {
    Sample() int
}

type ExampleImpl struct {
    sample int
}

func (example *ExampleImpl) Sample() int {
    return example.sample
}

func Hello() []Example {
    return []Example{&ExampleImpl{sample: 123}, &ExampleImpl{sample: 321}}
}

3. Build with gopy:

gopy build -output=out dummy.com/dum/hello

4. Run the following Python code:

>>> from out import hello
>>> output = hello.Hello()
>>> output[0].Sample()
panic: interface conversion: *hello.Example is not hello.Example: missing method Sample

goroutine 17 [running, locked to thread]:
main.hello_Example_Sample(0x2)
	/tmp/dum/out/hello.go:1230 +0xf9
zsh: IOT instruction (core dumped)  python