add docstring and fix unit test

Author: laurenyu

src/sagemaker/model.py

@@ -116,6 +116,10 @@ def __init__(
         self.model_kms_key = model_kms_key
 
     def _init_sagemaker_session_if_does_not_exist(self, instance_type):
+        """Set ``self.sagemaker_session`` to be a ``LocalSession`` or
+        ``Session`` if it is not already. The type of session object is
+        determined by the instance type.
+        """
         if self.sagemaker_session:
             return
 

tests/unit/test_model.py

@@ -579,16 +579,19 @@ def test_compile_model_for_cloud(sagemaker_session, tmpdir):
 @patch("sagemaker.session.Session")
 @patch("sagemaker.fw_utils.tar_and_upload_dir", MagicMock())
 def test_compile_creates_session(session):
+    session.return_value.boto_region_name = "us-west-2"
+
     model = DummyFrameworkModel(sagemaker_session=None)
     model.compile(
         target_instance_family="ml_c4",
         input_shape={"data": [1, 3, 1024, 1024]},
         output_path="s3://output",
         role="role",
         framework="tensorflow",
+        job_name="compile-model",
     )
 
-    assert model.sagemaker_sesion == session.return_value
+    assert model.sagemaker_session == session.return_value
 
 
 def test_check_neo_region(sagemaker_session, tmpdir):