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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def descendants(state, obj, level=0):
 """ Returns a flattened list tuples of DFS traversal of subtree from object that contains descendant object and it's depth """

    return sum([
        [(child, level)] + descendants(state, child, level + 1)
        for child in state[obj].children
    ], [])