code: public Object getAttribute(File file, String view, String attribute) {
      Object value = getAttributeInternal(file, view, attribute);
      if (value == null) {
        throw new IllegalArgumentException("invalid attribute for view '" + view + "': " + attribute);
      }
      return value;
    }
docs: Gets the value of the given attribute for the given view and file. Neither view nor attribute
  may have a ':' character.