code: function(tree, options) {
        if (!options) {
          options = {
            ext: '.css',
            importFormat: null, // to be initialized just bellow
            encoding: 'utf-8'
          };
        }
  
        if (!options.ext) {
          options.ext = '.css';
        }
  
        if (!options.importFormat) {
          if (options.ext === '.css') {
            options.importFormat = function(path) {
              return '@import "' + path + '";';
            };
          } else if (options.ext === '.less') {
            options.importFormat = function(path) {
              return '@import (less) "' + path + '";';
            };
          }
        }
  
        if (!options.encoding) {
          options.encoding = 'utf-8';
        }
  
        generate(tree, null, options);
      }
docs: Generate the files that contains @import rules on the given tree