code: function transform(args, opts, cb) {
    opts.config.relativeTo = opts.config.relativeTo || process.cwd();
    verbose = opts.config.verbose;
  
    var oldRequire = args[0];
  
    // Only look at non-local require statements
    if (oldRequire[0] !== ".") {
      log("Processing", oldRequire, "in", opts.file);
      var pathToRelative = path.relative(path.dirname(opts.file), opts.config.relativeTo);
  
      // Try and find a matching package
      var pkg = findPackage(opts.config, oldRequire);
      if (pkg) {
        var newRequire = "." + path.sep + path.join(pathToRelative, oldRequire.replace(pkg.name, pkg.src));
  
        // replace single backslashes with double backslashes for file paths in windows
        newRequire = newRequire.replace(/\\/gi, "/");
  
        log("Found pkg for", oldRequire, ":", pkg.name);
        log("Mapping to", newRequire);
        return cb(null, "require(\"" + newRequire + "\")");
      }
  
    }
  
    // Default behaviour - just return original
    return cb();
  }
docs: Transform function