function Input(css) {
        var opts = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {};

        _classCallCheck(this, Input);

        if (css === null || (typeof css === 'undefined' ? 'undefined' : _typeof(css)) === 'object' && !css.toString) {
            throw new Error('PostCSS received ' + css + ' instead of CSS string');
        }

        /**
         * @member {string} - input CSS source
         *
         * @example
         * const input = postcss.parse('a{}', { from: file }).input;
         * input.css //=> "a{}";
         */
        this.css = css.toString();

        if (this.css[0] === '\uFEFF' || this.css[0] === '\uFFFE') {
            this.css = this.css.slice(1);
        }

        if (opts.from) {
            if (/^\w+:\/\//.test(opts.from)) {
                /**
                 * @member {string} - The absolute path to the CSS source file
                 *                    defined with the `from` option.
                 *
                 * @example
                 * const root = postcss.parse(css, { from: 'a.css' });
                 * root.source.input.file //=> '/home/ai/a.css'
                 */
                this.file = opts.from;
            } else {
                this.file = _path2.default.resolve(opts.from);
            }
        }

        var map = new _previousMap2.default(this.css, opts);
        if (map.text) {
            /**
             * @member {PreviousMap} - The input source map passed from
             *                         a compilation step before PostCSS
             *                         (for example, from Sass compiler).
             *
             * @example
             * root.source.input.map.consumer().sources //=> ['a.sass']
             */
            this.map = map;
            var file = map.consumer().file;
            if (!this.file && file) this.file = this.mapResolve(file);
        }

        if (!this.file) {
            sequence += 1;
            /**
             * @member {string} - The unique ID of the CSS source. It will be
             *                    created if `from` option is not provided
             *                    (because PostCSS does not know the file path).
             *
             * @example
             * const root = postcss.parse(css);
             * root.source.input.file //=> undefined
             * root.source.input.id   //=> "<input css 1>"
             */
            this.id = '<input css ' + sequence + '>';
        }
        if (this.map) this.map.file = this.from;
    }
@param {string} css    - input CSS source
@param {object} [opts] - {@link Processor#process} options