Failure for functions which return result of another function invocation
Input
```py
def a():
	return "c"

def b():
    return a()

if __name__ == '__main__':
	print("OK")
```

Rust and Julia fail with exception `_typename_from_annotation` while processing `b`.
```py
>               raise Exception(typename, type(typename))
E               Exception: (None, <class 'NoneType'>)

py2many/pyrs/transpiler.py:130: in visit_Return
    return_type = self._typename_from_annotation(fndef, attr="returns")
py2many/clike.py:131: Exception
```

Dart, Go, Kotlin and Nim generate invalid syntax.