code: public boolean hasSlotIsNumber(final String slotName) {
          return hasSlot(slotName) && NumberUtils.isNumber(intentRequest.getIntent().getSlot(slotName).getValue());
      }
docs: Checks if a slot is contained in the intent request and its value is a number.
  @param slotName name of the slot to look after
  @return True, if the slot exists in the intent request and is a number.