function _isInAtRule(ctx) {
        var state = _getContextState(ctx);
        if (!state || !state.context) {
            return false;
        }
        return (state.context.type === "atBlock_parens");
    }
@private
Checks if the current cursor position is inside an at-rule
@param {editor:{CodeMirror}, pos:{ch:{string}, line:{number}}, token:{object}} context
@return {boolean} true if the context is in property value