An environment defines the concrete actor context, reference and timer times for a specific actor framework, such as Pekko or the deterministic simulation testing framework.

A bit of theory: This type utilizes F-bounded polymorphism, meaning that Env is parameterized over its own subtypes. This enables passing the implementing type as an argument to the superclass, facilitating the use of more specific argument and return types where subtypes of Env are present. Another commonly used pattern for this use case is the type-class pattern (also known as ad-hoc polymorphism), you can read more about both here: https://stackoverflow.com/questions/59813323/advantages-of-f-bounded-polymorphism-over-typeclass-for-return-current-type-prob