def parse_option_string(s):
    if not isinstance(s, str):
        return None
    options = {}
    for token in s.split(';'):
        pieces = token.split('=')
        if len(pieces) == 1:
            option, value = pieces[0], ""
        elif len(pieces) == 2:
            option, value = pieces
        else:
            raise ValueError((s) % "Plot option string '%s' is malformed.")
        options[option.strip()] = value.strip()
    return options
dataset/ETHPy150Open sympy/sympy/sympy/plotting/pygletplot/util.py/parse_option_string/swapped operands of `%`