Returns list of joined members (User objects).

def get_joined_members(self):
        """Returns list of joined members (User objects)."""
        if self._members:
            return list(self._members.values())
        response = self.client.api.get_room_members(self.room_id)
        for event in response["chunk"]:
            if event["content"]["membership"] == "join":
                user_id = event["state_key"]
                self._add_member(user_id, event["content"].get("displayname"))
        return list(self._members.values())