Is there an easy way to determine which methods don't have mappings registered yet?
When we built our framework, we decided to throw exceptions when method mappings weren't found. We had exceptions when the target object and arguments were immutable, and that made it rare to see the exceptions come up in practice. This
allowed us to find out right away if an expression was going to work without testing each expression by itself.
It would be nice of there was a way to get some sort of debug output on failed observability when ExpressionObserver is used to build an observer tree.