I want to send notifications programatically in odoo8.

According to the post below, 

      https://www.odoo.com/nl_NL/forum/help-1/question/how-to-send-a-message-programmatically-3389  

I modified the code to new api version as below:

post_vars = {'subject': "Message subject", 'body': "Message body", 'partner_ids': [(4, 3)],}
thread_pool = self.env['mail.thread']
thread_pool.message_post(False, type="notification", subtype="mt_comment", **post_vars)

But I got the following error.
TypeError: message_post() got multiple values for keyword argument 'body'.

If  I removed the False parameter, thread_id will be [], and I got index error for the following code in message_post()

So, how to call message_post() with new api ?