Law of Demeter (weak form).  Inside a method, it is only permitted
to access or send messages to the following objects:
- 1.
 - The arguments associated with the method being executed (including the self
object).
 - 2.
 - Instance variables for the receiver of the method.
 - 3.
 - Global variables.
 - 4.
 - Temporary variables created inside the method.