[Python] Better JSON Serialization and Marshaling

Description

Currently, the Python API client relies on our own deserialiser to convert JSON string back into Python objects with support of attribute mapping. For other generators (e.g. Java, C#), we're leveraging 3rd-party libraries/modules to handle serialization/deserialization between objects and JSON strings

We would like to evaluate different Python modules to perform similar tasks instead of maintaining our own serialization/deserialisation logic:

• Kim: JSON Serialization and Marshaling framework

If anyone has comments/suggestions or want to contribute to this enhancement, please reply to let us know. Thank you.