resolve comments

sdk/cosmos/azure-cosmos/azure/cosmos/_change_feed/change_feed_state.py

@@ -405,10 +405,11 @@ def from_initial_state(
         change_feed_start_from = (
             ChangeFeedStartFromInternal.from_start_time(change_feed_state_context.get("startTime")))
 
-        assert feed_range is not None
-        return cls(
-            container_link=container_link,
-            container_rid=collection_rid,
-            feed_range=feed_range,
-            change_feed_start_from=change_feed_start_from,
-            continuation=None)
+        if feed_range is not None:
+            return cls(
+                container_link=container_link,
+                container_rid=collection_rid,
+                feed_range=feed_range,
+                change_feed_start_from=change_feed_start_from,
+                continuation=None)
+        raise RuntimeError("feed_range is empty")

sdk/cosmos/azure-cosmos/azure/cosmos/_feed_range.py

@@ -32,18 +32,6 @@ class FeedRange(ABC):
     """Represents a single feed range in an Azure Cosmos DB SQL API container.
 
     """
-
-    def to_string(self) -> str:
-        """
-        Get a json representation of the feed range.
-        The returned json string can be used to create a new feed range from it.
-
-        :return: A json representation of the feed range.
-        :rtype: str
-        """
-
-        return self._to_base64_encoded_string()
-
     @staticmethod
     def from_string(json_str: str) -> 'FeedRange':
         """
@@ -76,14 +64,26 @@ def _to_base64_encoded_string(self) -> str:
         # Convert the Base64 bytes to a string
         return base64_bytes.decode('utf-8')
 
-class FeedRangeEpk (FeedRange):
+class FeedRangeEpk(FeedRange):
     type_property_name = "Range"
 
     def __init__(self, feed_range: Range) -> None:
         if feed_range is None:
             raise ValueError("feed_range cannot be None")
 
         self._feed_range = feed_range
+        self._base64_encoded_string = None
+
+    def __str__(self) -> str:
+        """Get a json representation of the feed range.
+           The returned json string can be used to create a new feed range from it.
+
+        :return: A json representation of the feed range.
+        """
+        if self._base64_encoded_string is None:
+            self._base64_encoded_string = self._to_base64_encoded_string()
+
+        return self._base64_encoded_string
 
     def _to_dict(self) -> Dict[str, Any]:
         return {
@@ -95,7 +95,7 @@ def _to_feed_range_internal(self) -> 'FeedRangeInternal':
 
     @classmethod
     def _from_json(cls, data: Dict[str, Any]) -> 'FeedRange':
-        if data.get(cls.type_property_name):
-            feed_range = Range.ParseFromDict(data.get(cls.type_property_name))
-            return cls(feed_range)
-        raise ValueError(f"Can not parse FeedRangeEPK from the json, there is no property {cls.type_property_name}")
+        try:
+            return cls(Range.ParseFromDict(data[cls.type_property_name]))
+        except KeyError as e:
+            raise ValueError(f"Can not parse FeedRangeEPK from the json, there is no property {cls.type_property_name}") from e