docs: def subdir_path(directory, relative):
      """Returns a file path relative to another path."""
      item_bits = directory.split(os.sep)
      relative_bits = relative.split(os.sep)
      for i, _item in enumerate(item_bits):
          if i == len(relative_bits) - 1:
              return os.sep.join(item_bits[i:])
          else:
              if item_bits[i] != relative_bits[i]:
                  return None
  
      return None