def add_file()

in client/securedrop_client/state/state.py [0:0]


    def add_file(self, cid: ConversationId, fid: FileId) -> None:
        file = File(fid)  # store references to the same object
        if fid not in self._files:
            self._files[fid] = file

        if cid not in self._conversation_files:
            self._conversation_files[cid] = []

        file_is_known = False
        for known_file in self._conversation_files[cid]:
            if fid == known_file.id:
                file_is_known = True
        if not file_is_known:
            self._conversation_files[cid].append(file)
            if cid == self._selected_conversation:
                self.selected_conversation_files_changed.emit()