Return the maximum value in this histogram.

        If there are no values in the histogram at all, return 600.

        Returns:
            int: The maximum value in the histogram.

def max(self):
        """Return the maximum value in this histogram.

        If there are no values in the histogram at all, return 600.

        Returns:
            int: The maximum value in the histogram.
        """
        if len(self._data) == 0:
            return 600
        return next(iter(reversed(sorted(self._data.keys()))))