code: public boolean removeAll(Collection<T> trans, Collection<I> items) {
  		if (trans == null || trans.isEmpty() || items == null || items.isEmpty())
  			return false;
  		return matrix.removeAll(allTransactions.convert(trans).indices(), allItems.convert(items).indices());
  	}
docs: Removes the pairs obtained from the Cartesian product of transactions and
  items
  
  @param trans
  collection of transactions
  @param items
  collection of items
  @return <code>true</code> if the set set has been changed