Regex_expand_selection.py

def expand_selection(self, states: Set[int]):
    expanded = set()
    to_expand = list(states)
    while to_expand:
        s = to_expand.pop()
        expanded.add(s)
        if s < len(self.nodes)  and self.stars[s]:
            if s+1 not in expanded:
                states.add(s+1)
                to_expand.append(s+1)