as far as I can tell by the way the project is bundled, if you are using the release version of the project (like the one in the CND or the dist folder) you cannot access them, because they are only defined directly in the function that uses them. So they are not exposed in any property or anything. (see image from the bundled file below)

Note: As mentioned in @Aifos answer, it was available but since version 2, Plotly no longer exposes .d3 property so if you use last version you will get an error
If you need them I'd recommend you to simply import the file yourself from the src file