def sentence_from_graph(dependency_graph):
    """ get original sentence from a dependency graph
    
    :param dependency_graph: nltk dependency graph
    :return: original English sentence
    """
    words = [dependency_graph.get_by_address(i)['word']
             for i in sorted(dependency_graph.nodes)
             if dependency_graph.get_by_address(i)['word'] is not None]
    return " ".join(words)