Contexts

[sebinsua]

• A context may be generated automatically as the object is transformed.
• A selector shall be passed a key-value object context.
• $contextKey may access the same key within the context.
• Define the list of context variables that we can expect to use in a selector.
• By default, the second argument of the makeSelector function, too. This means transformFn is either the 2nd argument or the 3rd argument.