code: def item_set_goto(itemset, inputsymbol, productionset):
      
      resultset = LR0ItemSet()
      for item in itemset.itemlist:
          if item.next_symbol() == inputsymbol:
              newitem = LR0Item(item.rule, item.position + 1)
              resultset.append_item(newitem)
      return _build_item_closure(resultset, productionset)
docs: returns an itemset
      locate inside itemset every element with inputsymbol following cursor
      for every located item, append its itemclosure