private static @NotNull String getExternalDocumentationRoot(@NotNull Sdk sdk) {
    final String versionString = sdk.getVersionString();
    if (versionString != null && StringUtil.startsWithIgnoreCase(versionString, "jython")) {
      return "http://jython.org/docs/library/";
    }
    final String pyVersion = PythonDocumentationProvider.pyVersion(versionString);
    StringBuilder urlBuilder = new StringBuilder("https://docs.python.org/");
    if (pyVersion != null) {
      urlBuilder.append(pyVersion).append("/");
    }
    if (pyVersion != null && (pyVersion.startsWith("2.4") || pyVersion.startsWith("2.5"))) {
      urlBuilder.append("lib/");
    }
    else {
      urlBuilder.append("library/");
    }
    return urlBuilder.toString();
  }
private static @NotNull String getExternalDocumentationRoot(@NotNull Sdk sdk)