ImportError from rasa_core_sdk

Hi, I am trying to adapt the FormAction code from rasa_core/examples/formbot at master · RasaHQ/rasa_core · GitHub, but I am struggling with the imports from rasa_core_sdk. I previously had a custom action working well, but when I try to do from rasa_core_sdk import FormAction (or ActionExecutionRejection) I get an ImportError: cannot import name ‘FormAction’

Do I somehow have the wrong version of rasa_core_sdk installed (it says it is 0.11.5)? I am not very experienced in the Python world!

thanks, J