zulip-bots: Add BotStorage Protocol.

The `BotStorage` Protocol is created to add a common type to all
storage classes.

Note: Protocol is imported from `typing_extensions` as `typing`
doesn't provide Protocol for python <= 3.7.

zulip_bots/setup.py

@@ -65,6 +65,7 @@ setuptools_info = dict(
         'html2text',
         'lxml',
         'BeautifulSoup4',
+        'typing_extensions',
     ],
 )
 

zulip_bots/zulip_bots/lib.py

@@ -9,7 +9,7 @@ import re
 
 
 from typing import Any, Optional, List, Dict, IO, Text
-
+from typing_extensions import Protocol
 from zulip import Client, ZulipError
 
 
@@ -102,6 +102,16 @@ class BotIdentity:
         self.email = email
         self.mention = '@**' + name + '**'
 
+class BotStorage(Protocol):
+    def put(self, key: Text, value: Any) -> None:
+        ...
+
+    def get(self, key: Text) -> Any:
+        ...
+
+    def contains(self, key: Text) -> bool:
+        ...
+
 class ExternalBotHandler:
     def __init__(
         self,