updated generate_tfrecord.py to work with tensorflow 2

Author: TannerGilbert

generate_tfrecord.py

@@ -5,7 +5,12 @@
 import os
 import io
 import pandas as pd
-import tensorflow as tf
+
+from tensorflow.python.framework.versions import VERSION
+if VERSION >= "2.0.0a0":
+    import tensorflow.compat.v1 as tf
+else:
+    import tensorflow as tf
 
 from PIL import Image
 from object_detection.utils import dataset_util