code: def append(cls, d, s, filter=Filter()):
          
          for item in s:
              if item in filter:
                  d.append(item)
docs: Append schema object's from B{s}ource list to
          the B{d}estination list while applying the filter.
          @param d: The destination list.
          @type d: list
          @param s: The source list.
          @type s: list
          @param filter: A filter that allows items to be appended.
          @type filter: L{Filter}