Imports enable a Sentinel policy to access reusable libraries and external data and functions. Anyone can write their own custom import. Imports are what enable Sentinel policies to do more than look at only local context for making policy decisions.
Imports are extremely powerful. They enable policy decision based on arbitrary external information. For example, a behavior coming into a system can be allowed or denied based on information from a separate system where the two systems can be unaware of each other.
The example below shows a concrete example. For the example, imagine that the import calendar allows access to engineer calendars. This import only exists for the purpose of this example and at the time of writing is not a real available import.