Function extract_references 

pub fn extract_references(expr: &Expression) -> References

Extract all fact and rule references from an expression.

Recursively walks the expression tree to find all references to facts and rules. Useful for dependency analysis and validation.

Examples

Expression: price * quantity
Returns: facts = ["price", "quantity"], rules = []

Expression: base_amount + adjustment?
Returns: facts = ["base_amount"], rules = ["adjustment"]