def _enforce_no_overlap(self, start_at=0):
        """Enforce that no ranges overlap in internal storage."""
        i = start_at
        while i+1 < len(self.data):
            if self.data[i][1] >= self.data[i+1][0]:
                # beginning of i+1-th range is contained in i-th range
                if self.data[i][1] < self.data[i+1][1]:
                    # i+1-th range is longer, thus enlarge i-th range
                    self.data[i][1] = self.data[i+1][1]

                # removed contained range
                del self.data[i+1]
            i += 1
Enforce that no ranges overlap in internal storage.