Rasa/duckling return bad request 400

I just download duckling docker image (docker pull rasa/duckling) and run it. Console terminal showed docker pull rasa/duckling.

However, when I sent a unit test case (curl -XPOST http://localhost:8000/parse --data ‘locale=en_GB&text=yesterday’). The following error message was shown: 400 - Bad Request

What did I do wrong? I thought docker should be very simple to use.

Basically, my question is whether the current duckling docker image works. Thanks.