'Detect the filter modifier'

def _get_filter_modifier(self, field):

    tokens = field.split(FIELD_SEPARATOR)
    if (len(tokens) == 1):
        return (field, '')
    if (tokens[(-1)] in self.FILTER_OPERATORS.keys()):
        return (u'.'.join(tokens[:(-1)]), tokens[(-1)])
    return (u'.'.join(tokens), '')
