How to use the csso.parse function in csso

packCommentToken(' [WARN] Recursion: ' + context.map(relpath).join(' -> ') + ' -> ' + relpath(filename) + ' '),
          [{}, 's', '\n\n']
        ];
      }

      treeConsole.log('# [OK] ' + relpath(filename));

      content = fs.readFileSync(filename, 'utf-8');
      context.push(filename);
    }

    if (context.length)
      content = content.replace(/^|\n/g, "$&" + offset);

    // parse css into tree
    var cssTree = csso.parse(content, 'stylesheet');

    // add header
    cssTree.splice(2, 0,
      [{}, 's', offset],
      packCommentToken('\n ' + offset + '* ' + filename + ' content injection\n ' + offset),
      [{}, 's', '\n']
    );
    cssTree.push(
      [{}, 's', '\n\n']
    );

    treeConsole.incDeep();
    processCssTree(cssTree, baseURI, context);
    treeConsole.decDeep();

    if (!isInlineStyle)

// collect 

function rebaseCss(css, file, config) {
    // Handle empty CSS files
    if (config.noCss || !css.trim()) {
        return css;
    }
    var ast;
    try {
        ast = CSSO.parse(css);
    } catch (exception) {
        config.out.warn("CSS parse error: " + file.path);
        config.out.warn(exception.message);
        return css;
    }

    var worklist = [ast];
    while (worklist.length) {
        var node = worklist.pop(), quote;
        if (node[0] === "uri") {
            var value = node[1], uri;
            if (value[0] === "raw") {
                uri = value[1];
                quote = "";
            } else if (value[0] === "string") {
                // remove quotes (first and last character)

// skip selectors that match more than once if option onlyMatchedOnce is enabled
      continue;
    }

    for (var selectedElIndex in selectedEls) {
      var selectedEl = selectedEls[selectedElIndex];

      // empty defaults in case there is no style attribute
      var elInlineStyleAttr = { name: 'style', value: '', prefix: '', local: 'style' },
        elInlineStyles = '';

      if (selectedEl.hasAttr('style')) {
        elInlineStyleAttr = selectedEl.attr('style');
        elInlineStyles = elInlineStyleAttr.value;
      }
      var inlineCssAst = csso.parse(elInlineStyles, { context: 'block' });

      // merge element(inline) styles + matching <style> styles
      var newInlineCssAst = csso.parse('', { context: 'block' }); // for an empty css ast (in block context)

      var mergedDeclarations = [];
      var _fetchDeclarations = function (node, item) {
        if (node.type === 'Declaration') {
          mergedDeclarations.push(item);
        }
      };
      var itemRulesetNodeCloned = csso.clone(selectorItem.rulesetNode);
      // clone to prevent leaking declaration references (csso.translate(...))
      csso.walk(itemRulesetNodeCloned, _fetchDeclarations);
      csso.walk(inlineCssAst, _fetchDeclarations);

      // sort by !important(ce)</style>

for (var selectedElIndex in selectedEls) {
      var selectedEl = selectedEls[selectedElIndex];

      // empty defaults in case there is no style attribute
      var elInlineStyleAttr = { name: 'style', value: '', prefix: '', local: 'style' },
        elInlineStyles = '';

      if (selectedEl.hasAttr('style')) {
        elInlineStyleAttr = selectedEl.attr('style');
        elInlineStyles = elInlineStyleAttr.value;
      }
      var inlineCssAst = csso.parse(elInlineStyles, { context: 'block' });

      // merge element(inline) styles + matching <style> styles
      var newInlineCssAst = csso.parse('', { context: 'block' }); // for an empty css ast (in block context)

      var mergedDeclarations = [];
      var _fetchDeclarations = function (node, item) {
        if (node.type === 'Declaration') {
          mergedDeclarations.push(item);
        }
      };
      var itemRulesetNodeCloned = csso.clone(selectorItem.rulesetNode);
      // clone to prevent leaking declaration references (csso.translate(...))
      csso.walk(itemRulesetNodeCloned, _fetchDeclarations);
      csso.walk(inlineCssAst, _fetchDeclarations);

      // sort by !important(ce)
      var mergedDeclarationsSorted = stable(mergedDeclarations, function (declarationA, declarationB) {
        var declarationAScore = ~~declarationA.data.value.important, // (cast boolean to number)
          declarationBScore = ~~declarationB.data.value.important; //  "</style>