code: def rel_path_from_chan_path(chan_path, channeldir, windows=False):
      
      if windows:
          chan_path_list = chan_path.split('\\')
      else:
          chan_path_list = chan_path.split('/')
      chan_path_list.pop(0)  # remove the channel root dir
      rel_path = os.path.join(channeldir, *chan_path_list)
      return rel_path
docs: Convert `chan_path` as obtained from a metadata provider into a `rel_path`
      suitable for accessing the file from the current working directory, e.g.,
      >>> rel_path_from_chan_path('Open Stax/Math', 'content/open_stax_zip/Open Stax')
      'content/open_stax_zip/Open Stax/Math'