'Accept an arbitrary set of assertion key/value pairs.  For
each assertion key/value pair assert that the renderer
(eg. :func:`pyramid.renderers.render_to_response`)
received the key with a value that equals the asserted
value. If the renderer did not receive the key at all, or the
value received by the renderer doesn\'t match the assertion
value, raise an :exc:`AssertionError`.'

def assert_(self, **kw):

    for (k, v) in kw.items():
        myval = self._received.get(k, _marker)
        if (myval is _marker):
            myval = self._implementation._received.get(k, _marker)
            if (myval is _marker):
                raise AssertionError(('A    value    for    key    "%s"    was    not    passed    to    the    renderer' % k))
        if (myval != v):
            raise AssertionError(('\nasserted    value    for    %s:    %r\nactual    value:    %r' % (k, v, myval)))
    return True
