code: def find_notebook(fullname, path=None):
      
      name = fullname.rsplit('.', 1)[-1]
      if not path:
          path = ['']
      for d in path:
          nb_path = os.path.join(d, name + ".ipynb")
          if os.path.isfile(nb_path):
              return nb_path
          # let import Notebook_Name find "Notebook Name.ipynb"
          nb_path = nb_path.replace("_", " ")
          if os.path.isfile(nb_path):
              return nb_path
docs: find a notebook, given its fully qualified name and an optional path
  
      This turns "foo.bar" into "foo/bar.ipynb"
      and tries turning "Foo_Bar" into "Foo Bar" if Foo_Bar
      does not exist.