Question: Why validation for region, resource and stage

[smiletolead]

This is about the need for validation of the methodArn. The methodArn value is split and then the parts like region, resource and stage are validated. We see if resource and stage are empty or not. Just wondering in what cases stage and region can be empty? Also, is there a possibility that resource is having invalid characters? Currently it is checked agains the regex which allows numbers, alphabets, -, . and *.