Type hinting

projector.py

@@ -11,15 +11,17 @@ class ProjectorSerial(SerialDevice):
 
         super().__init__(serial_port, baudrate)
 
-    def send_command(self, command: str, verbose: bool = False, device_id: str = "ZZ"):
+    def send_command(
+        self, command: str, verbose: bool = False, device_id: str = "ZZ"
+    ) -> str:
         assert device_id in ["01", "02", "03", "04", "05", "06", "ZZ"]
 
         full_command = f"\x02AD{device_id};{command}\x03"
 
         return super().send_command(full_command, verbose)
 
-    def power_on(self):
+    def power_on(self) -> None:
         self.send_command("PON")
 
-    def power_off(self):
+    def power_off(self) -> None:
         self.send_command("POF")

serialdevice.py

@@ -7,7 +7,7 @@ class SerialDevice:
         self.serial_port: str = serial_port
         self.baudrate = baudrate
 
-    def send_command(self, command: str, verbose: bool = False):
+    def send_command(self, command: str, verbose: bool = False) -> str:
         with Serial(self.serial_port, self.baudrate, timeout=1) as s:
             if verbose:
                 print("Send:", command)