code: def rel(path, parent=None, par=False):
    
  
    try:
      res = os.path.relpath(path, parent)
    except ValueError:
      # Raised eg. on Windows for differing drive letters.
      if not par:
        return abs(path)
      raise
    else:
      if not par and not issub(res):
        return abs(path)
      return res
docs: Takes *path* and computes the relative path from *parent*. If *parent* is
    omitted, the current working directory is used.
  
    If *par* is #True, a relative path is always created when possible.
    Otherwise, a relative path is only returned if *path* lives inside the
    *parent* directory.