def __get__(self, instance, owner):
        if instance is None:
            # Document class being used rather than a document object
            return self

        # Get value from document instance if available
        return instance._data.get(self.name)
Descriptor for retrieving a value from a field in a document.
dataset/ETHPy150Open MongoEngine/mongoengine/mongoengine/base/fields.py/BaseField.__get__