There is a way to define MongoDB collection schema using mongoose in NodeJS. Mongoose verifies the schema at the time of running the queries.
I have been unable to find a similar thing for Motor in Python/Tornado. Is there a way to achieve a similar effect in Motor, or is there a package which can do that for me?
No there isn't. Motor is a MongoDB driver, it does basic operations but doesn't provide many conveniences. An Object Document Mapper (ODM) library like MongoTor, built on Motor, provides higher-level features like schema validation.
I don't vouch for MongoTor. Proceed with caution. Consider whether you really need an ODM: mongodb's raw data format is close enough to Python types that most applications don't need a layer between their code and the driver.