dvh.py Line 252: return self.cumulative.relative_volume**.differential**

[shaokn]

@property
    def relative_volume(self):
        """Return a relative volume DVH."""
        volume_units = relative_units
        if self.volume_units == relative_units:
            return self
        # Convert back to cumulative before returning a relative volume
        elif self.dvh_type == 'differential':
            return self.cumulative.relative_volume.differential
        else:
            return DVH(**dict(
                self.__dict__,
                counts=100 * self.counts /
                       (1 if (self.max == 0) else self.counts.max()),
                       volume_units=volume_units))

dvh.py
Line 252: return self.cumulative.relative_volume**.differential**
It seems that ".differential" should be removed from this code.