Class Function
The Function class represents a block of code to be called, which may or may not produce a value. Function values are first-class, and can be passed around as arguments, placed into a List, and so on.
The arguments of a Function are denoted within parentheses, with an optional colon at the end to denote the value returned:
Function(Integer): String (return String).
Function(String, String) (no value returned).