如何解决：TypeError：__ init __（）得到了一个意外的关键字参数＆＃39; safe＆＃39;

Question

我在Python中使用MongoAlchemy和Flask建立了一个MongoDB数据库。问题是，当我尝试将对象保存到数据库中时，我收到此错误，并且我在互联网上找不到答案。问题似乎与保存功能的参数安全有关，但它不应以任何方式影响它，因为该参数是可选的。这就是我的代码的样子：

    p1 = People(Name='Chis', Age=21, Password='abc', Vms=[

            {'Name': 'Virtual1',
             'Status': 'Active'},

            {'Name': 'Virtual2',
             'Status': 'Inactive'},

            {'Name': 'Virtual3',
             'Status': 'Active'}
        ])

    p1.save()

这是完整的错误日志：

Traceback (most recent call last):
  File "app.py", line 64, in <module>
    app = create_app()
  File "app.py", line 26, in create_app
    insert_db.populateTables()
  File "/home/chis/IDEs/pycharm-community-2017.1.4/Projects/REST_API/api/blueprints/db/insert_db.py", line 45, in populateTables
    p1.save(safe=None)
  File "/home/chis/IDEs/pycharm-community-2017.1.4/Projects/FlaskServer/env/local/lib/python2.7/site-packages/flask_mongoalchemy/__init__.py", line 275, in save
    self._session.insert(self, safe=safe)
  File "/home/chis/IDEs/pycharm-community-2017.1.4/Projects/FlaskServer/env/local/lib/python2.7/site-packages/mongoalchemy/session.py", line 172, in insert
    self.add(item, safe=safe)
  File "/home/chis/IDEs/pycharm-community-2017.1.4/Projects/FlaskServer/env/local/lib/python2.7/site-packages/mongoalchemy/session.py", line 188, in add
    return self.flush()
  File "/home/chis/IDEs/pycharm-community-2017.1.4/Projects/FlaskServer/env/local/lib/python2.7/site-packages/mongoalchemy/session.py", line 414, in flush
    result = op.execute()
  File "/home/chis/IDEs/pycharm-community-2017.1.4/Projects/FlaskServer/env/local/lib/python2.7/site-packages/mongoalchemy/ops.py", line 97, in execute
    return self.collection.save(self.data, safe=self.safe)
  File "/home/chis/IDEs/pycharm-community-2017.1.4/Projects/FlaskServer/env/local/lib/python2.7/site-packages/pymongo/collection.py", line 2440, in save
    write_concern = WriteConcern(**kwargs)
TypeError: __init__() got an unexpected keyword argument 'safe'

编辑：包含People类的脚本

from init_db import db


class People(db.Document):
    Name = db.StringField()
    Age = db.IntField()
    Password = db.StringField()
    Vms = db.AnythingField()

为未来的观众编辑：我设法通过安装旧版本的pymongo（最好是2.9.0）解决了这个问题。