@Override
    public boolean has(TensorAddress address) {
        var block = index.blockOf(address);
        int denseOffset = index.denseOffsetOf(address);
        return (block != null && denseOffset >= 0 && denseOffset < block.cells.length);
    }
Returns the value at the given address
vespajlib/src/main/java/com/yahoo/tensor/MixedTensor.java