docs: def coalesce(self):
  		"""
  		Sort the elements of the list into ascending order, and merge
  		continuous segments into single segments.  Segmentlist is
  		modified in place.  This operation is O(n log n).
  		"""
  		self.sort()
  		i = j = 0
  		n = len(self)
  		while j < n:
  			lo, hi = self[j]
  			j += 1
  			while j < n and hi >= self[j][0]:
  				hi = max(hi, self[j][1])
  				j += 1
  			if lo != hi:
  				self[i] = segment(lo, hi)
  				i += 1
  		del self[i : ]
  		return self