from pymongo import MongoClient
c = MongoClient()
db = c.test
pipeline = [ { "$project": { "operationType": "insert", "ns.viewOn": "db.coll" } } ]
cursor = db.inventory.watch(pipeline=pipeline)
document = next(cursor)

from pymongo import MongoClient
c = MongoClient()
db = c.test
db.inventory.insert_one({"username": "bob"})

---------------------------------------------------------------------------
OperationFailure                          Traceback (most recent call last)
Input In [7], in <cell line: 1>()
----> 1 document = next(cursor)

File ~/pymongo/change_stream.py:262, in ChangeStream.next(self)
    230 """Advance the cursor.
    231
    232 This method blocks until the next change document is returned or an
   (...)
    259 Raises :exc:`StopIteration` if this ChangeStream is closed.
    260 """
    261 while self.alive:
--> 262     doc = self.try_next()
    263     if doc is not None:
    264         return doc

File ~/pymongo/change_stream.py:316, in ChangeStream.try_next(self)
    313 # Attempt to get the next change with at most one getMore and at most
    314 # one resume attempt.
    315 try:
--> 316     change = self._cursor._try_next(True)
    317 except (ConnectionFailure, CursorNotFound):
    318     self._resume()

File ~/pymongo/command_cursor.py:292, in CommandCursor._try_next(self, get_more_allowed)
    290 """Advance the cursor blocking for at most one getMore command."""
    291 if not len(self.__data) and not self.__killed and get_more_allowed:
--> 292     self._refresh()
    293 if len(self.__data):
    294     return self.__data.popleft()

File ~/pymongo/command_cursor.py:218, in CommandCursor._refresh(self)
    216     dbname, collname = self.__ns.split('.', 1)
    217     read_pref = self.__collection._read_preference_for(self.session)
--> 218     self.__send_message(
    219         self._getmore_class(dbname,
    220                             collname,
    221                             self.__batch_size,
    222                             self.__id,
    223                             self.__collection.codec_options,
    224                             read_pref,
    225                             self.__session,
    226                             self.__collection.database.client,
    227                             self.__max_await_time_ms,
    228                             self.__sock_mgr, False))
    229 else:  # Cursor id is zero nothing else to return
    230     self.__die(True)

File ~/pymongo/command_cursor.py:164, in CommandCursor.__send_message(self, operation)
    162 client = self.__collection.database.client
    163 try:
--> 164     response = client._run_operation(
    165         operation, self._unpack_response, address=self.__address)
    166 except OperationFailure as exc:
    167     if exc.code in _CURSOR_CLOSED_ERRORS:
    168         # Don't send killCursors because the cursor is already closed.

File ~/pymongo/mongo_client.py:1201, in MongoClient._run_operation(self, operation, unpack_res, address)
   1196 def _cmd(session, server, sock_info, read_preference):
   1197     return server.run_operation(
   1198         sock_info, operation, read_preference, self._event_listeners,
   1199         unpack_res)
-> 1201 return self._retryable_read(
   1202     _cmd, operation.read_preference, operation.session,
   1203     address=address, retryable=isinstance(operation, message._Query))

File ~/pymongo/mongo_client.py:1302, in MongoClient._retryable_read(self, func, read_pref, session, address, retryable)
   1300             assert last_error is not None
   1301             raise last_error
-> 1302         return func(session, server, sock_info, read_pref)
   1303 except ServerSelectionTimeoutError:
   1304     if retrying:
   1305         # The application may think the write was never attempted
   1306         # if we raise ServerSelectionTimeoutError on the retry
   1307         # attempt. Raise the original exception instead.

File ~/pymongo/mongo_client.py:1197, in MongoClient._run_operation.<locals>._cmd(session, server, sock_info, read_preference)
   1196 def _cmd(session, server, sock_info, read_preference):
-> 1197     return server.run_operation(
   1198         sock_info, operation, read_preference, self._event_listeners,
   1199         unpack_res)

File ~/pymongo/server.py:130, in Server.run_operation(self, sock_info, operation, read_preference, listeners, unpack_res)
    128         first = docs[0]
    129         operation.client._process_response(first, operation.session)
--> 130         _check_command_response(first, sock_info.max_wire_version)
    131 except Exception as exc:
    132     if publish:

File ~/pymongo/helpers.py:166, in _check_command_response(response, max_wire_version, allowable_errors, parse_write_concern_error)
    163 elif code == 43:
    164     raise CursorNotFound(errmsg, code, response, max_wire_version)
--> 166 raise OperationFailure(errmsg, code, response, max_wire_version)

OperationFailure: assertion src/mongo/db/exec/document_value/value.h:478, full error: {'ok': 0.0, 'errmsg': 'assertion src/mongo/db/exec/document_value/value.h:478', 'code': 8, 'codeName': 'UnknownError', '$clusterTime': {'clusterTime': Timestamp(1649786952, 1), 'signature': {'hash': b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00', 'keyId': 0}}, 'operationTime': Timestamp(1649786952, 1)}