The `::attribute` declaration with type checking is defined [here](https://github.com/heyzooi/Xcodeproj/blob/6d252de344ea8c5ed7ec2e8ef850286cd67982c2/lib/xcodeproj/project/object_attributes.rb#L266) and it is reserved to indicate which attributes mirror the ones defined by Xcode in an Xocdeproj. In this case I would just use: `attr_reader`. Also this method can me be marked as private.