This should be (part of) a python docstring, not comments:
```python
    """
    Usage:
        class BlogEntrySerializer(MongoEngineModelSerializer):
            model = BlogEntry
            depth = 1
            related_model_validations = {'Category': Category, 'author': User}
    """
```

See [pep 257](http://legacy.python.org/dev/peps/pep-0257/) for more detail.