import itertools


def leaf_strategy(doc):
    """
    Should return an arrays of variable names based on leaf strategy

    :param doc: spacy document
    :return Array of strings
    """

    suggestions = dfs(doc[0])
    return suggestions


def dfs(graph, result=[], output=[]):
    flag = False
    for u in graph.children:
        flag = True
        dfs(u, [*result, graph.text], output)
    if flag is False:
        output.append([*result, graph.text])
    return output