code: public boolean hasSlot(final String slotName) {
          return intentRequest != null && intentRequest.getIntent().getSlots().containsKey(slotName);
      }
docs: Checks if a slot is contained in the intent request. This is no guarantee that the slot
  value is not null.
  @param slotName name of the slot to look after
  @return True, if the slot exists in the intent request