["id", "name", "wkt", "created", "radius", "round"]

{"id":"1", "name":"a", "round":5}
{"id":"2", "wkt": "POINT(1.1)", "created":"2018-22-11T10:00:00"}
{"id":"3", "radius":3}

for line in lines:
    line_dict = json.loads(line)
    for key in keys:
        if not key in line_dict:
            line_dict[key] = None
    yield line_dict