Train error，maybe something wrong in bounding_box.py

[Aliengmx]

@mjanusz
Hi, if I used python2.7 I got the same syntax error with #19.
And then I transform to python 3.7 I got another new error:
def _required(bbox: Optional[BoundingBox]) -> BoundingBox:
NameError: name 'Optional' is not defined

Is any help for this issue?

[oradomskyi]

Hi @Aliengmx

add import line below to the beginning of file bounding_box.py

from typing import Optional