def rename_slash_blackslash(path_input, slash_in_path=r'\\', slash_in_outpath='/'):
    """
    replace the "\" or "\\" in path name to "/" 

    Parameters
    ----------

    path_input       : file path of files that need to be rename.

    slash_in_path    : "\\" or r"\\" in input path name.

    slash_in_outpath : '/' in output path name .

    Tips
    ----------
    the path_input need to be unescaped.When we add a letter 'r' in the beginning  of the path_input, the path input will be unescaped,
    such as path_input=r"G:\data\test_20210618\reconstruction_image".

    """
    path_output = path_input.replace(slash_in_path, slash_in_outpath)
    return path_output