code: def add_media(self, mrl):
          
          if isinstance(mrl, basestring):
              mrl = (self.get_instance() or get_default_instance()).media_new(mrl)
          return libvlc_media_list_add_media(self, mrl)
docs: Add media instance to media list.
          
          The L{lock} should be held upon entering this function.
          @param mrl: a media instance or a MRL.
          @return: 0 on success, -1 if the media list is read-only.