code: def points_with_surrounding_gaps(points):
      
      points_with_gaps = []
      last_point = -1
      for point in points:
          if last_point + 1 == point:
              pass
          elif last_point + 2 == point:
              points_with_gaps.append(last_point + 1)
          else:
              points_with_gaps.append(last_point + 1)
              points_with_gaps.append(point - 1)
          points_with_gaps.append(point)
          last_point = point
      return points_with_gaps
docs: This function makes sure that any gaps in the sequence provided have stopper points at their beginning
      and end so a graph will be drawn with correct 0 ranges. This is more efficient than filling in all points
      up to the maximum value. For example:
  
      input: [1,2,3,10,11,13]
      output [1,2,3,4,9,10,11,12,13]