code: private Set<PackageRef> collectPackageDependencies() {
  		Set<PackageRef> referencedPackages = new HashSet<PackageRef> ();
  		for (TypeRef newReferencedType:importedReferencedTypes) {
  			PackageRef packageRef = newReferencedType.getPackageRef();
  			if (referencedPackages.contains(packageRef))			// package already known
  				continue;
  			referencedPackages.add(packageRef);
  			System.out.println("Add package: " + packageRef.getFQN());
  		}
  		return referencedPackages;
  	}
docs: Collect the referenced packages information from the referenced classes information
  @return referencedPackages