code: def by_maintainer(cls, session, maintainer_name):
          
          return cls.find(session,
                          join=(cls.maintainers),
                          where=(User.login == maintainer_name,),
                          order_by=cls.name)
docs: Get package from a given maintainer name.
  
          :param session: SQLAlchemy session
          :type session: :class:`sqlalchemy.Session`
  
          :param maintainer_name: maintainer username
          :type maintainer_name: unicode
  
          :return: package instances
          :rtype: generator of :class:`pyshop.models.Package`