Addressing Issue aws#1184 - create Session by default

Author: matthewfollegot

src/sagemaker/model.py

@@ -20,6 +20,7 @@
 import sagemaker
 from sagemaker import fw_utils, local, session, utils, git_utils
 from sagemaker.fw_utils import UploadedCode
+from sagemaker.session import Session
 from sagemaker.transformer import Transformer
 
 LOGGER = logging.getLogger("sagemaker")
@@ -129,7 +130,7 @@ def __init__(
         self.env = env or {}
         self.name = name
         self.vpc_config = vpc_config
-        self.sagemaker_session = sagemaker_session
+        self.sagemaker_session = sagemaker_session or Session()
         self._model_name = None
         self.endpoint_name = None
         self._is_compiled_model = False