def get(self, id, pk='id', deleted=False):
        try:
            if pk == 'id':
                id = int(id)
            if deleted:
                spec = {pk: id}
            else:
                spec = {pk: id, 'data': {'$exists': 1}}
            fields = {'_id': 0}
            row = self.db.docs.find_one(spec, fields)
        except Exception as e:
            raise DatabaseException(e)
        if row:
            return Document(**row)
        raise NotFoundError('%s %s not found' % (pk, id))
async def echo_server(loop, address, unix):
    if unix:
        sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
    else:
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    sock.bind(address)
    sock.listen(5)
    sock.setblocking(False)
    if PRINT:
        print('Server listening at', address)
    with sock:
        while True:
            client, addr = await loop.sock_accept(sock)
            if PRINT:
                print('Connection from', addr)
            loop.create_task(echo_client(loop, client))