code: function (str, options, cb) {
      var self = this;
      if (self.cache(options)) return cb(null, self.cache(options));
      if (options.filename) {
        options.paths = options.paths || [dirname(options.filename)];
      }
  
      // If this.cache is enabled, compress by default
      if (options.compress !== true && options.compress !== false) {
        options.compress = options.cache || false;
      }
  
      var initial = this.engine(str);
  
      // Special handling for stylus js api functions
      // given { define: { foo: 'bar', baz: 'quux' } }
      // runs initial.define('foo', 'bar').define('baz', 'quux')
  
      var allowed = ['set', 'include', 'import', 'define', 'use'];
      var special = {}
      var normal = clone(options);
      for (var v in options) {
        if (allowed.indexOf(v) > -1) { special[v] = options[v]; delete normal[v]; }
      }
  
      // special options through their function names
      for (var k in special) {
        for (var v in special[k]) { initial[k](v, special[k][v]); }
      }
  
      // normal options through set()
      for (var k in normal) {
        initial.set(k, normal[k]);
      }
  
      initial.render(function (err, res) {
        if (err) return cb(err);
        self.cache(options, res);
        cb(null, res);
      });
    }
docs: always runs synchronously