toggle method
Toggle whether a selection is still in the storage structure.
Implementation
void toggle(List<T> selection) {
_checkSelection(selection);
final index = combinatorics.indexOf(selection).toInt(),
byte = index ~/ 8,
bit = index % 8,
mask = 1 << bit;
_data.setUint8(byte, _data.getUint8(byte) ^ mask);
}