How to use the placebo.serializer.Format.JSON function in placebo

def test_get_deserializer_json(self):
        ser = get_deserializer(Format.JSON)
        self.assertEqual(ser, _deserialize_json)

def test_roundtrip_json(self):
        ser = get_serializer(Format.JSON)
        deser = get_deserializer(Format.JSON)
        fp = StringIO()
        ser(date_sample, fp)
        fp.seek(0)
        obj = deser(fp)
        self.assertEqual(obj, date_sample)

    def __init__(self, prefix=None, debug=False, record_format=Format.JSON):
        if debug:
            self._set_logger(__name__, logging.DEBUG)

        record_format = record_format.lower()
        if record_format not in Format.ALLOWED:
            LOG.warning("Record format not allowed. Falling back to default.")
            record_format = Format.DEFAULT

        self._serializer = get_serializer(record_format)
        self._filename_re = re.compile(r'.*\..*_(?P\d+).{0}'.format(
            record_format))
        self._record_format = record_format
        self.prefix = prefix
        self._uuid = str(uuid.uuid4())
        self._data_path = None
        self._mode = None