add interpreter to graph (#1347)

### What problem does this PR solve?

#918 

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

api/db/__init__.py

@@ -91,4 +91,9 @@ class FileSource(StrEnum):
     KNOWLEDGEBASE = "knowledgebase"
     S3 = "s3"
 
+
+class CanvasType(StrEnum):
+    ChatBot = "chatbot"
+    DocBot = "docbot"
+
 KNOWLEDGEBASE_FOLDER_NAME=".knowledgebase"