Need help on opening mobs inventory when the mob is tamed and the owner is sneaking.

It's annoying trying to feed a pet with inventory,  I tried making a procedure for it but the items in the inventory kept disappearing, instead I edited the code, where the override for the inventory is I wrote a line before the first 'if' : 

if (sourceentity.isShiftKeyDown()) {

and a bracket at the close  " } "      

                                                                                                                                                  }

example:

@Override

    public InteractionResult mobInteract(Player sourceentity, InteractionHand hand) {

        ItemStack itemstack = sourceentity.getItemInHand(hand);

        InteractionResult retval = InteractionResult.sidedSuccess(this.level().isClientSide());

if (sourceentity.isShiftKeyDown()) {
        if (sourceentity instanceof ServerPlayer serverPlayer) {

            NetworkHooks.openScreen(serverPlayer, new MenuProvider() {

                @Override

                public Component getDisplayName() {

                    return Component.literal("thief");

                }



                @Override

                public AbstractContainerMenu createMenu(int id, Inventory inventory, Player player) {

                    FriendlyByteBuf packetBuffer = new FriendlyByteBuf(Unpooled.buffer());

                    packetBuffer.writeBlockPos(sourceentity.blockPosition());

                    packetBuffer.writeByte(0);

                    packetBuffer.writeVarInt(ThiefEntity.this.getId());

                    return new ThiefGUIMenu(id, inventory, packetBuffer);

                }

            }, buf -> {

                buf.writeBlockPos(sourceentity.blockPosition());

                buf.writeByte(0);

                buf.writeVarInt(this.getId());

            });

        }

}

It has worked so far, and he hasn't stolen anything. drops the inventory on death

problem solved I think

(sourceentity.isShiftKeyDown() && (this.isTame() && this.isOwnedBy(sourceentity)))