'Merge dependences (messages, attachments, ...). These dependences will be
transfered to `self`, the most important lead.
:param opportunities : recordset of opportunities to transfert. Does
not include `self`.'

@api.multi
def merge_dependences(self, opportunities):

    self.ensure_one()
    self._merge_notify(opportunities)
    self._merge_opportunity_history(opportunities)
    self._merge_opportunity_attachments(opportunities)
