Send to Facebook typing indications

async def _send_typing(self, request: Request, stack: Stack):
        """
        Send to Facebook typing indications
        """

        active = stack.get_layer(lyr.Typing).active

        msg = ujson.dumps({
            'recipient': {
                'id': request.conversation.fbid,
            },
            'sender_action': 'typing_on' if active else 'typing_off',
        })

        headers = {
            'content-type': 'application/json',
        }

        params = {
            'access_token': self._access_token(request),
        }

        post = self.session.post(
            MESSAGES_ENDPOINT,
            params=params,
            data=msg,
            headers=headers,
        )

        logger.debug('Sending: %s', msg)

        async with post as r:
            await self._handle_fb_response(r)