code: def notebook_executed(pth):
      
  
      nb = nbformat.read(pth, as_version=4)
      for n in range(len(nb['cells'])):
          if nb['cells'][n].cell_type == 'code' and \
                  nb['cells'][n].execution_count is None:
              return False
      return True
docs: Determine whether the notebook at `pth` has been executed.