diff --git a/zulip/integrations/slack/slackdata2zulipdata.py b/zulip/integrations/slack/slackdata2zulipdata.py
index 3f81fb0..aef0d84 100755
--- a/zulip/integrations/slack/slackdata2zulipdata.py
+++ b/zulip/integrations/slack/slackdata2zulipdata.py
@@ -6,17 +6,26 @@ import sys
 import argparse
 import shutil
 import subprocess
-import zipfile
+
+from typing import Any, Dict, List
+# stubs
+user_profile_stub = Dict[str, Any]
+added_users_stub = Dict[str, int]
 
 
 # Transported from https://github.com/zulip/zulip/blob/master/zerver/lib/export.py
-def rm_tree(path):
-    # type: (str) -> None
+def rm_tree(path: str) -> None:
     if os.path.exists(path):
         shutil.rmtree(path)
 
-def users2zerver_userprofile(slack_dir, realm_id, timestamp, domain_name):
-    # type: () -> None
+def users2zerver_userprofile(slack_dir: str, realm_id: int, timestamp: Any,
+                             domain_name: str) -> (List[user_profile_stub], added_users_stub):
+    """
+    Returns:
+    1. zerver_userprofile, which is a list of user profile
+    2. added_users, which is a dictionary to map from slack user id to zulip
+       user id
+    """
     print('######### IMPORTING USERS STARTED #########\n')
     users = json.load(open(slack_dir + '/users.json'))
     zerver_userprofile = []
@@ -215,7 +224,7 @@ def channelmessage2zerver_message(slack_dir, channel, added_users, added_channel
             zulip_message = dict(
                 sending_client=1,
                 rendered_content_version=1,  # This is Zulip-specific
-                has_image=msg['has_image'],
+                has_image=msg.get('has_image', False),
                 subject=channel,  # This is Zulip-specific
                 pub_date=msg['ts'],
                 id=msg_id_count,
@@ -226,13 +235,11 @@ def channelmessage2zerver_message(slack_dir, channel, added_users, added_channel
                 rendered_content=text,  # slack doesn't cache this
                 recipient=added_channels[channel],
                 last_edit_time=None,
-                has_link=msg['has_link'])
+                has_link=msg.get('has_link', False))
             zerver_message.append(zulip_message)
     return zerver_message
 
-def main(slack_zip_file):
-    # type: (str) -> None
-
+def main(slack_zip_file: str) -> None:
     slack_dir = slack_zip_file.replace('.zip', '')
     subprocess.check_call(['unzip', slack_zip_file])
     # with zipfile.ZipFile(slack_zip_file, 'r') as zip_ref: