This is already the standard stack based DFS?

  def dfs(graph, source):
    n = len(graph)
    visited = set()
    stack = [source]
    
    while stack:
      node = stack.pop()
      if node in visited:
        continue 
      visited.add(node)
      for nbr in graph[node]:
        stack.append(nbr)

So I don't know what all the confusion is about...