Add Missing Type Annotations

Author: tcfranks

adafruit_scd4x.py

@@ -216,7 +216,7 @@ def data_ready(self) -> bool:
         return not ((self._buffer[0] & 0x07 == 0) and (self._buffer[1] == 0))
 
     @property
-    def serial_number(self) -> tuple(int):
+    def serial_number(self) -> Tuple(int, int):
         """Request a 6-tuple containing the unique serial number for this sensor"""
         self._send_command(_SCD4X_SERIALNUMBER, cmd_delay=0.001)
         self._read_reply(self._buffer, 9)