Updated return type logic for OD detections (#147)

* Added logic to return list

* lint fixes

python/ml_wrappers/model/image_model_wrapper.py

@@ -314,7 +314,7 @@ def _get_device(device: str) -> str:
     :rtype: str
     """
     if (device in [member.value for member in Device]
-       or type(device) == int
+       or type(device) is int
        or device.isdigit()
        or device is None):
         if device == Device.AUTO.value:
@@ -525,7 +525,7 @@ def predict(self, x, iou_threshold: float = 0.5, score_threshold: float = 0.5):
         """
         detections = []
         for image in x:
-            if type(image) == Tensor:
+            if type(image) is Tensor:
                 raw_detections = self._model(
                     image.to(self._device).unsqueeze(0))
             else:
@@ -543,7 +543,10 @@ def predict(self, x, iou_threshold: float = 0.5, score_threshold: float = 0.5):
 
                 detections.append(image_predictions.detach().cpu().numpy()
                                   .tolist())
-        return np.array(detections)
+        try:
+            return np.array(detections)
+        except ValueError:
+            return detections
 
     def predict_proba(self, dataset, iou_threshold=0.1):
         """Predict the output probability using the wrapped model.
@@ -657,7 +660,10 @@ def predict(self, dataset: pd.DataFrame, iou_threshold: float = 0.5,
             detections.append(
                 image_predictions.detach().cpu().numpy().tolist())
 
-        return np.array(detections)
+        try:
+            return np.array(detections)
+        except ValueError:
+            return detections
 
     def predict_proba(self, dataset: pd.DataFrame,
                       iou_threshold=0.1) -> np.ndarray: