Backwards-incompatible: many is passed as a keyword argument to methods decorated with pre_load, post_load, pre_dump, post_dump, and validates_schema. partial is passed as a keyword argument to methods decorated with pre_load, post_load and validates_schema. **kwargs should be added to all decorated methods.
So there will be no error like : TypeError: dump_user() got an unexpected keyword argument 'many'
This could solve the issue : https://github.com/gothinkster/flask-realworld-example-app/issues/25
Based on marshmallow change log
So there will be no error like : TypeError: dump_user() got an unexpected keyword argument 'many'