Plugins dependency

I'm trying to create a new plugin to retrieve how many weeks has an specific year.

The algorithm relies on methods that are already created in others plugins (`daysInYear`, `isLeapYear`, `dayOfYear`). How we should treat this dependency?

I see various options

1. The dependant plugin (`weeksInYear` in this case) also includes the other plugins. The worst case scenario would be that some plugins are loaded twice. If this would be the case, a warning message could be shown in the console saying something like `The plugin .... has been loaded twice`.
2. If the others plugins aren't loaded, do not load this one, and show an error message through console saying something like `This plugins .... must be included in order to this plugin works`
3. Duplicate the functionality of the plugins inside the dependant. This would make the plugin agnostic to other plugins, but the amount of code would increase, I think, needlessly.

Since the main goal of this lib is to remain small, my preferred option is the 1st one. Any thoughts?