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()