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