code: public static SafeStyleSheet fromConstant(@CompileTimeConstant final String styleSheet) {
      if (styleSheet.length() == 0) {
        return SafeStyleSheet.EMPTY;
      }
      for (int i = 0; i < styleSheet.length(); i++) {
        if (styleSheet.charAt(i) == '<') {
          throw new IllegalArgumentException(
              "Forbidden '<' character in style sheet string: " + styleSheet);
        }
      }
      return create(styleSheet);
    }
docs: Creates a SafeStyleSheet from the given compile-time constant string {@code style}.
  
  <p>{@code styleSheet} must not have any &lt; characters in it so that the syntactic
  structure of any surrounding CSS and HTML is not affected.
  
  @throws IllegalArgumentException if {@code styleSheet} contains &lt;