In class `\Magento\ConfigurableProduct\Block\Product\View\Type\Configurable` there is the function bellow.
     
    /**
     * Returns additional values for js config, con be overridden by descendants
     *
     * @return array
     */
    protected function _getAdditionalConfig()
    {
        return [];
    }

How one could "rewrite" (use plugin) it since it is protected.
I wanted to add additional data in this function because it is used in "getJsonConfig" function.

I guess if I'd want to make a plugin I would need to use getJsonConfig function because it is public. Which comes back to my question.
Should `_getAdditionalConfig()` be used by end users or it's just for Magento core use ?

**Edit**
I could use a preference for this block class.

**Edit 2**
Adding a preference for this block class doesn't seem to work

**Edit 3**
Made a plugin on `\Magento\ConfigurableProduct\Block\Product\View\Type\Configurable`. Function used is `getJsonConfig`.