     
     // MARK: Properties
     
-    var invisibles: [Invisible] = [.newLine, .tab, .fullwidthSpace]
+    private let invisibles: [Invisible] = [.newLine, .tab, .fullwidthSpace]
     
     
     

        guard let string = self.string(for: obj) else { return nil }
        
        let attributedString = NSMutableAttributedString(string: string, attributes: attrs)
        let attributes: [NSAttributedString.Key: Any] = [.foregroundColor: NSColor.tertiaryLabelColor]
        
        for (index, codeUnit) in string.utf16.enumerated() {
            guard

                self.invisibles.contains(invisible)
                else { continue }
            
            let attributedInvisible = NSAttributedString(string: invisible.usedSymbol, attributes: attributes)
            attributedString.replaceCharacters(in: NSRange(index...index), with: attributedInvisible)
        }
        
        return attributedString
