@classmethod
def _discover_params(cls):
    """
        Returns a dict where filter keyword is key, and class is value.
        To handle param alias (maxRecords or max_records), both versions are
        added.
        """
    try:
        return cls.filters
    except AttributeError:
        filters = {}
        for param_class_name in dir(cls):
            param_class = getattr(cls, param_class_name)
            if hasattr(param_class, 'kwarg'):
                filters[param_class.kwarg] = param_class
                filters[param_class.param_name] = param_class
        cls.filters = filters
    return cls.filters
