code: public static SARLPackageExplorerPart getFromActivePerspective() {
  		final IWorkbenchPage activePage = JavaPlugin.getActivePage();
  		if (activePage == null) {
  			return null;
  		}
  		final IViewPart view = activePage.findView(ID_PACKAGES);
  		if (view instanceof PackageExplorerPart) {
  			return (SARLPackageExplorerPart) view;
  		}
  		return null;
  	}
docs: Returns the package explorer part of the active perspective. If
  there isn't any package explorer part <code>null</code> is returned.
  
  @return the package explorer from the active perspective