both self.options, options or even @options work here. 

At first, when I developed this feature, I needed to pass a "context" when parsing a liquid document. Unfortunately, that was not possible with the current Liquid implementation. 
But, for the next version of Liquid (the coming 3.0.0), there is an option parameter when constructing a blog/tag and I'm using it as an alias for my previous context parameter. 
The name and the use of **options** can be misleading here.