Check if mention exists

inbox.py

@@ -1311,6 +1311,15 @@ def sendToGroupMembers(session,baseDir: str,handle: str,port: int,postJsonObject
         # add mention to tag list
         if not postJsonObject['object']['tag']:
             postJsonObject['object']['tag']=[]
+        # check if the mention already exists
+        mentionExists=False
+        for mention in postJsonObject['object']['tag']:
+            if mention['type']=='Mention':
+                if mention.get('href'):
+                    if mention['href']==sendingActor:
+                        mentionExists=True
+        if not mentionExists:
+            # add the mention of the original sender
             postJsonObject['object']['tag'].append({
                 'href': sendingActor,
                 'name': senderStr,