delegate=True on the Many2one field, now replaces _inherits usage

reflect fields with delegate=True in dictionary self._inherits

set it to ``True`` to make fields of the target model

accessible from the current model (corresponds to ``_inherits``)

If 'delegate': False  whether self implements delegation

delegate: set it to True to make fields of the target model accessible from the current model (corresponds to _inherits)
 

Please read the following link for batter understanding

http://stackoverflow.com/questions/832536/when-to-use-delegation-instead-of-inheritance