def check(cls, dic):
        """
        Convert a dictionary name->string into a dictionary name->value
        by converting the string. If the name does not correspond to a
        known parameter, just ignore it and print a warning.
        """
        res = {}
        for name, text in dic.items():
            try:
                p = getattr(cls, name)
            except AttributeError:
                logging.warning('Ignored unknown parameter %s', name)
            else:
                res[name] = p.validator(text)
        return res