Yes, I understand the rationale, but for example, there is another method called 'is_valid_uuid'.   If the project ID of Keystone was indeed that UUID format, and that method is called instead, should that method have been named 'is_valid_keystone_project_id'?  If the KS changed its format, then we need to have a method that validates that particular format and keep the validation for hex format in tact.  If this method is used in several places that are not just for KS ID validation (since it doesn't care if the input came from KS or not), you don't want to change this method only because KS changed its format.  I think your reasoning above is exactly why I think this method need not be tied to KS.  You could name it as 'keystone_project_id' if it does something specific to Keystone project though, but looking at the method, that doesn't seem to be case.