Common interface for data container classes (Python 3)

 The ItemAdapter class is a wrapper for data container objects, providing a
 common interface to handle objects of different types in an uniform manner,
 regardless of their underlying implementation.
 .
 Currently supported types are:
  * dict
  * scrapy.item.Item
  * dataclass-based classes
  * attrs-based classes
 .
 This is the Python 3 version of the package.