def get_value(self, obj):
        """
        Returns the value of the object's attribute.
        """
        if self.attribute is None:
            return None

        attrs = self.attribute.split('__')
        value = obj

        for attr in attrs:
            try:
                value = getattr(value, attr, None)
            except (__HOLE__, ObjectDoesNotExist):
                # needs to have a primary key value before a many-to-many
                # relationship can be used.
                return None
            if value is None:
                return None

        # RelatedManager and ManyRelatedManager classes are callable in
        # Django >= 1.7 but we don't want to call them
        if callable(value) and not isinstance(value, Manager):
            value = value()
        return value
dataset/ETHPy150Open django-import-export/django-import-export/import_export/fields.py/Field.get_value