code: public Number extractNumber() throws DevFailed {
          logger.debug(LOG_EXTRACTING, this);
          final Object result = attributeImpl.extract();
          if (!Number.class.isAssignableFrom(result.getClass())) {
              throw DevFailedUtils.newDevFailed(TANGO_WRONG_DATA_ERROR, THIS_ATTRIBUTE_MUST_BE_A_JAVA_LANG_NUMBER);
          }
          return (Number) result;
      }
docs: Extract value in a Number without conversion
  
  @return
  @throws DevFailed