'Splits `filters` into a tuple of two lists:
a list of filters to be added to the SQL query
and a list of functional filters to be applied after the SQL query.'

def _split_filters(self, filters):

    (orm_filters, fn_filters) = ([], [])
    if (filters is None):
        return (orm_filters, fn_filters)
    if (not isinstance(filters, list)):
        filters = [filters]
    for filter_ in filters:
        if self._is_fn_filter(filter_):
            fn_filters.append(filter_)
        else:
            orm_filters.append(filter_)
    return (orm_filters, fn_filters)
