Hello,

You can find this method code in odoo addons module. for eg. in mail thread module use below code

@api.multi
def message_post_with_view(self, views_or_xmlid, **kwargs):
    """ Helper method to send a mail / post a message using a view_id to
    render using the ir.qweb engine. This method is stand alone, because
    there is nothing in template and composer that allows to handle
    views in batch. This method should probably disappear when templates
    handle ir ui views. """
    values = kwargs.pop('values', None) or dict()
    try:
        from odoo.addons.http_routing.models.ir_http import slug
        values['slug'] = slug
    except ImportError:
        values['slug'] = lambda self: self.id
    if isinstance(views_or_xmlid, pycompat.string_types):
        views = self.env.ref(views_or_xmlid, raise_if_not_found=False)
    else:
        views = views_or_xmlid
    if not views:
        return
    for record in self:
        values['object'] = record
        rendered_template = views.render(values, engine='ir.qweb', minimal_qcontext=True)
        kwargs['body'] = rendered_template
        record.message_post_with_template(False, **kwargs)

Thanks