This method is only defined for package data apps. It is used to set up (initiate) the package data store of a package.
Using the package data store is optional for any package.
If package data apps exist within a package, they are to be stored under
{PKG}/sys/package/packageData. Later versions will be appended to
that list. At any time, that last app in that list must implement the
.InitPackageData so that the package can be installed on websites.
It will be called after installing the package, or in case no package data app existed at that time, then at the first update when a package data app is found.
When executing the method, the variable f points to the package data store at
/sys/packageData/PACKAGE_NAME.
This method will be called at most once during the lifecycle of an installed package.
Read more on packages.