code: def merge_intervals(intervals):
      
      if intervals is None:
          return None
      intervals.sort(key=lambda i: i[0])
      out = [intervals.pop(0)]
      for i in intervals:
          if out[-1][-1] >= i[0]:
              out[-1][-1] = max(out[-1][-1], i[-1])
          else:
              out.append(i)
      return out
docs: Merge intervals in the form of a list.