docs: public IPAddressString adjustPrefixLength(int adjustment) {
  		if(isPrefixOnly()) {
  			int newBits = adjustment > 0 ? Math.min(IPv6Address.BIT_COUNT, getNetworkPrefixLength() + adjustment) : Math.max(0, getNetworkPrefixLength() + adjustment);
  			return new IPAddressString(IPAddressNetwork.getPrefixString(newBits), validationOptions);
  		}
  		IPAddress address = getAddress();
  		if(address == null) {
  			return null;
  		}
  		if(adjustment == 0) {
  			return this;
  		}
  		Integer prefix = address.getNetworkPrefixLength();
  		if(prefix != null && prefix + adjustment < 0 && address.isPrefixBlock()) {
  			return new IPAddressString(IPAddress.SEGMENT_WILDCARD_STR, validationOptions);
  		}
  		return address.adjustPrefixLength(adjustment).toAddressString();
  	}