Let's say that you have one addon that does basically what you want it to do.  However, what it does when it inherits another class should be tweaked. For instance, account/account_invoice.py has:

class mail_compose_message(models.Model):
    _inherit = 'mail.compose.message'

    @api.multi
    def send_mail(self):
        context = self._context
        if context.get('default_model') == 'account.invoice' and \
                context.get('default_res_id') and context.get('mark_invoice_as_sent'):
            invoice = self.env['account.invoice'].browse(context['default_res_id'])
            invoice = invoice.with_context(mail_post_autofollow=True)
            invoice.write({'sent': True})
            invoice.message_post(body=_("Invoice sent"))
        return super(mail_compose_message, self).send_mail()
 

If I inherit mail_compose_message and update something, say set 'sent' to False, the account_invoice code runs afterwards and sets it back to True.

In this example, how do I inherit send_mail() method AFTER the code above is run to set sent or mail_post_autofollow to False?