Where to create the function that can be called from several tools?

I created a python toolbox with a bunch of tools. I have to create a list and a dictionary (very long) for almost all the tools - The list and dictionary have the same elements for all the tools that will use them. I was thinking I could create a function to first create this list and dictionary and then call if from the tools that will use them. If this is possible, where in the file, should I create this function? thank you!!!