def __init__(self, value_type=str, default=SENTINAL):
    if (value_type not in PARSERS):
        raise ValueTypeError()
    self._parser = PARSERS.get(value_type)
    self._default = default
def __init__(self, value_type=str, default=SENTINAL):
    if (value_type not in PARSERS):
        raise ValueTypeError()
    self._parser = PARSERS.get(value_type)
    self._default = default