code: def copy_attr(f1, f2):
      
      copyit = lambda x: not hasattr(f2, x) and x[:10] == 'PACKAGING_'
      if f1._tags:
          pattrs = [tag for tag in f1._tags if copyit(tag)]
          for attr in pattrs:
              f2.Tag(attr, f1.GetTag(attr))
docs: copies the special packaging file attributes from f1 to f2.