issue with StateMachineBehaviour not present in namespace UnityEngine

Hi, I am trying to run an old project that hasn’t been updated or loaded in Unity since 5.5.

I get an error when loading the project, that complain about

The type name ‘StateMachineBehaviour’ could not be found in the namespace ‘UnityEngine’.

Probably Unity API did change a bit since when the project was built, so I am trying to fix all the issues related to namespaces.

Does anyone know where was this moved to? And if it is deprecated, what should I use instead?

hello, it continue being inside that namespace but maybe has changed the way of doing it? here is an example of usage in 2018 version