Cache client as instance attribute in property@ decorator. (aws#1668)

* Remove property@ decorator from ABC definition.

* Cache client as instance attribute in @Property.

* Fix flake8 issue.

---------

Co-authored-by: Joseph Zhang <[email protected]>

Author: cj-zhang

src/sagemaker/serve/spec/inference_base.py

@@ -18,12 +18,18 @@
 class CustomOrchestrator(ABC):
     """Templated class to standardize sync entrypoint-based inference scripts"""
 
+    def __init__(self):
+        self._client = None
+
     @property
     def client(self):
         """Boto3 SageMaker runtime client to use with custom orchestrator"""
-        from boto3 import Session
+        if not hasattr(self, "_client"):
+            from boto3 import Session
+
+            self._client = Session().client("sagemaker-runtime")
 
-        return Session().client("sagemaker-runtime")
+        return self._client
 
     @abstractmethod
     def handle(self, data, context=None):