Fix typo in obj detection's running_pets.md

object_detection/g3doc/running_pets.md

@@ -284,7 +284,7 @@ command from `tensorflow/models/object_detection`:
 ``` bash
 # From tensorflow/models
 gsutil cp gs://${YOUR_GCS_BUCKET}/train/model.ckpt-${CHECKPOINT_NUMBER}.* .
-python object_detection/export_inference_graph \
+python object_detection/export_inference_graph.py \
     --input_type image_tensor \
     --pipeline_config_path object_detection/samples/configs/faster_rcnn_resnet101_pets.config \
     --checkpoint_path model.ckpt-${CHECKPOINT_NUMBER} \