pub trait Resources<'a> {
type Library: Library + LibraryBuilder<'a>;
fn get_package(&self, package_id: u8) -> Option<&Self::Library>;
fn get_mut_package(&mut self, package_id: u8) -> Option<&mut Self::Library>;
fn get_main_package(&self) -> Option<&Self::Library>;
fn is_main_package(&self, package_id: u8) -> bool;
}