code: public static Observable<List<File>> createFileFromUri(final Context context,
        final ArrayList<Uri> uris) {
      return createFileFromUri(context, uris, MimeMap.UrlConnection);
    }
docs: /*
  Create a copy of the files found under the provided ArrayList of Uris, in the Library's cache folder.
  
  The mime type of the resource will be determined by URLConnection.guessContentTypeFromName() method.