def relative_filename(filename: str) -> str:
    """Return the relative form of `filename`.

    The file name will be relative to the current directory when the
    `set_relative_directory` was called.

    """
    fnorm = os.path.normcase(filename)
    if fnorm.startswith(RELATIVE_DIR):
        filename = filename[len(RELATIVE_DIR):]
    return filename
Return the relative form of `filename`.

    The file name will be relative to the current directory when the
    `set_relative_directory` was called.

    
coverage/files.py