code: public String readAsString(final String separator, final String endSeparator) throws DevFailed {
          update();
          return extractToString(separator, endSeparator);
      }
docs: Read attribute and convert it to a String with separators
  
  @param separator
  between each value (for SPECTRUM and IMAGE only)
  @param endSeparator
  between each dimension (for IMAGE only)
  @return The formatted string
  @throws DevFailed