Marshmallow is a framework-agnostic library for converting complex datatypes,
such as objects, to and from primitive Python datatypes.
Marshmallow schemas can be used to:
* Validate input data.
* Deserialize input data to app-level objects.
* Serialize app-level objects to primitive Python types. The serialized objects
can then be rendered to standard formats such as JSON for use in an HTTP API.
Python 3 version.
