A helper function to create a ReferenceCell object from an integer. ReferenceCell objects are "singletons" (actually, "multitons" – there are multiple, but they are only a handful and these are all that can be used). What is then necessary is to have a way to create these with their internal id to distinguish the few possible ones in existence. We could do this via a public constructor of ReferenceCell, but that would allow users to create ones outside the range we envision, and we don't want to do that. Rather, the constructor that takes an integer is made private
but we have this one function in an internal namespace that is a friend of the class and can be used to create the objects.
Definition at line 611 of file reference_cell.h.