AI and DS Skills

In docplex CPO model:

I would like to define a transition matrix for Interval Variables

In some documentation I found a statement: "Transition times can be modeled using tuples with three elements. The first element is the interval variable type of one task, the second is the interval variable type of the other task and the third element of the tuple is the transition time from the first to the second. An integer interval variable type can be associated with each interval variable."
I have defined many interval variables in my model, but I cannot find out what an "interval variable type" is nor how to define it