date_unit must be one of (self._STAMP_UNITS)

Raise code

        if orient == "split":
            numpy = False

        if date_unit is not None:
            date_unit = date_unit.lower()
            if date_unit not in self._STAMP_UNITS:
                raise ValueError(f"date_unit must be one of {self._STAMP_UNITS}")
            self.min_stamp = self._MIN_STAMPS[date_unit]
        else:
            self.min_stamp = self._MIN_STAMPS["s"]

        self.numpy = numpy
        self.precise_float = precise_float
        self.convert_axes = convert_axes