code: def verify_duplicates(duplicates, uniques):
      
      for uniq1, uniq2 in itertools.combinations(uniques, 2):
          if same_intersection(uniq1, uniq2):
              raise ValueError("Non-unique intersection")
  
      counter = collections.Counter()
      for dupe in duplicates:
          matches = []
          for index, uniq in enumerate(uniques):
              if same_intersection(dupe, uniq):
                  matches.append(index)
          if len(matches) != 1:
              raise ValueError("Duplicate not among uniques", dupe)
  
          matched = matches[0]
          counter[matched] += 1
      for index, count in six.iteritems(counter):
          uniq = uniques[index]
          if count == 1:
              if (uniq.s, uniq.t).count(0.0) != 1:
                  raise ValueError("Count == 1 should be a single corner", uniq)
  
          elif count == 3:
              if (uniq.s, uniq.t) != (0.0, 0.0):
                  raise ValueError("Count == 3 should be a double corner", uniq)
  
          else:
              raise ValueError("Unexpected duplicate count", count)
docs: Verify that a set of intersections had expected duplicates.
  
      .. note::
  
         This is a helper used only by :func:`generic_intersect`.
  
      Args:
          duplicates (List[.Intersection]): List of intersections
              corresponding to duplicates that were filtered out.
          uniques (List[.Intersection]): List of "final" intersections
              with duplicates filtered out.
  
      Raises:
          ValueError: If the ``uniques`` are not actually all unique.
          ValueError: If one of the ``duplicates`` does not correspond to
              an intersection in ``uniques``.
          ValueError: If a duplicate occurs only once but does not have
              exactly one of ``s`` and ``t`` equal to ``0.0``.
          ValueError: If a duplicate occurs three times but does not have
              exactly both ``s == t == 0.0``.
          ValueError: If a duplicate occurs a number other than one or three
              times.