fix: Warn when calling nonexistent properties (#1370)

Author: speller26

src/braket/aws/aws_device.py

@@ -497,6 +497,12 @@ def properties(self) -> DeviceCapabilities:
 
         .. _amazon-braket-schemas-python: https://github.com/aws/amazon-braket-schemas-python
         """
+        if not self._properties:
+            warnings.warn(
+                "No device capabilities found;"
+                " please make sure you are using the latest version of amazon-braket-schemas.",
+                stacklevel=1,
+            )
         return self._properties
 
     @property

test/unit_tests/braket/aws/test_aws_device.py

@@ -693,7 +693,8 @@ def test_get_device_invalid_capabilities(arn):
     mock_session.region = RIGETTI_REGION
     device = AwsDevice(arn, mock_session)
     assert device is not None
-    assert device.properties is None
+    with pytest.warns(UserWarning):
+        assert device.properties is None
 
 
 MOCK_PULSE_MODEL_QPU_PULSE_CAPABILITIES_JSON_1 = {