@Override
    protected void onDeserialize(Deserializer buf) {
        super.onDeserialize(buf);
        numBits = buf.getInt(null);
    }
Sets the number of bits to operate on.

@param numBits The number of bits.
@return This, to allow chaining.
searchlib/src/main/java/com/yahoo/searchlib/expression/UnaryBitFunctionNode.java