text: import nbformat, os
  
  rootdir = "_build/jupyter"
  subdirs = ["dynamic_programming", "dynamic_programming_squared", "getting_started_julia", "more_julia", "multi_agent_models", "time_series_models", "tools_and_techniques"]
  forbidden_names = ["index.ipynb"]
  
  colab_markdown_text = open(os.path.join(rootdir, "_static", "includes", "colab-instructions.md")).read()
  colab_markdown_cell = nbformat.v4.new_markdown_cell(colab_markdown_text)
  
  colab_code_text = open(os.path.join(rootdir, "_static", "includes", "colab_code_cell.txt")).read()
  colab_code_cell = nbformat.v4.new_code_cell(colab_code_text)
  
  for dir in subdirs:
      path = os.path.join(rootdir, dir)
      nbs = os.listdir(path)
      for nb in nbs: 
          print(os.path.join(dir, nb))
          nb_dict = nbformat.read(os.path.join(path, nb), 4)
          nb_dict['cells'].insert(2, colab_markdown_cell)
          nb_dict['cells'].insert(3, colab_code_cell)
          nbformat.write(nb_dict, os.path.join(path, nb))