code: def cast_in(self, element):
          
          if _debug: SequenceOfAny._debug("cast_in %r", element)
  
          # make sure it is a list
          if not isinstance(element, List):
              raise EncodingError("%r is not a list" % (element,))
  
          t = TagList()
          element.encode(t)
  
          self.tagList.extend(t.tagList)
docs: encode the element into the internal tag list.