public void ParseToken(DslToken token)
        {
            if (token.TokenType != "constraint")
            {
                throw new FIQLException("Error while parsing a constraint : token " + token.ToString() + " is not an constraint.");
            }

            _selector = token.Groups["selector"];
            if (token.Groups.ContainsKey("comparison"))
            {
                _comparison = token.Groups["comparison"];
            }
            if (token.Groups.ContainsKey("argument"))
            {
                _argument = token.Groups["argument"];
            }
        }