def _decode_options(options):
    """Parse options given in str.

    When options = 'cutoff = 4.0', options is converted to {'cutoff': 4.0}.

    In this implementation (can be modified), using phonopy command line
    options, ``options`` is passed by  --fc-calc-opt such as::

       phonopy --hiphiveph --fc-calc-opt "cutoff = 4" ...

    """
    option_dict = {}
    for pair in options.split(","):
        key, value = [x.strip() for x in pair.split("=")]
        if key == "cutoff":
            option_dict[key] = float(value)
    return option_dict