code: def relative_path(path, from_file):
      
      if path is None:
          return None
      abs_path_target = absolute_path(path, from_file)
      abs_path_cwd = os.getcwd()
      if is_windows():
          # NOTE on Windows, if the two paths are on different drives,
          #      the notion of relative path is not defined:
          #      return the absolute path of the target instead.
          t_drive, t_tail = os.path.splitdrive(abs_path_target)
          c_drive, c_tail = os.path.splitdrive(abs_path_cwd)
          if t_drive != c_drive:
              return abs_path_target
      return os.path.relpath(abs_path_target, start=abs_path_cwd)
docs: Return the relative path of a file or directory, specified
      as ``path`` relative to (the parent directory of) ``from_file``.
  
      This method is intented to be called with ``__file__``
      as second argument.
  
      The returned path is relative to the current working directory.
  
      If ``path`` is ``None``, return ``None``.
  
      Example: ::
  
          path="res/foo.bar"
          from_file="/root/abc/def/ghi.py"
          cwd="/root"
          => "abc/def/res/foo.bar"
  
      :param string path: the file path
      :param string from_file: the reference file
      :rtype: string