def initialize_copy( original_obj )
      @vertices = Array.new(original_obj.vertices.size)
      for i in 0..@vertices.size-1
        @vertices[i] = original_obj.vertices[i].dup
      end
      @is_open = original_obj.is_open
    end
def initialize_copy( original_obj )
      @vertices = Array.new(original_obj.vertices.size)
      for i in 0..@vertices.size-1
        @vertices[i] = original_obj.vertices[i].dup
      end
      @is_open = original_obj.is_open
    end
[Input]
  _vertices_ should be Array of Vector3.
 [Output]
  return new instance of Polyline.