fix return type of cups.py

src/escpos/printer/cups.py

@@ -199,7 +199,7 @@ class CupsPrinter(Escpos):
         self.tmpfile.close()
         self.pending_job = False
 
-    def _read(self) -> List[int]:
+    def _read(self) -> bytes:
         """Return a single-item array with the accepting state of the print queue.
 
         states: idle = [3], printing a job = [4], stopped = [5]
@@ -207,8 +207,8 @@ class CupsPrinter(Escpos):
         printer = self.printers.get(self.printer_name, {})
         state = printer.get("printer-state")
         if not state:
-            return []
-        return [state]
+            return b''
+        return bytes((state,))
 
     def close(self) -> None:
         """Close CUPS connection.