In jinja2 templates used for llm prompts, it is possible to access nested json structures in the item, e.g. {{ input.concept.title }}. However, this is not possible for simple lookups like embedding_keys. This is both limiting, and a bit confusing. It would be awesome to use the same logic for lookups, not just straight item.get(key) for key in self.config.get("embedding_keys").

This could be done by using compile_expression from jinja2