使用NLTK捕获具有小写介词的专有名词

Question

我已经开始使用NLTK找到合适的名词了。但是，我很难找到其中包含小写介词的专有名词（人名和组织名称）。

例如，

The David Eccles School of Business at the University of Utah

变成（使用我的nltk POS标记器）：

David Eccles School, Business, University

另一个例子：

The United Nations Economic and Social Council's Economic Commission for Africa

变为

United Nations Economic, Social Council, Economic Commission, Africa

有什么建议吗？

我正在考虑的一些事情（将所有介词和所有介词都大写）

    tokens2 = nltk.word_tokenize(x)
    tags = nltk.pos_tag(tokens2)
    res = nltk.ne_chunk(tags)
    tree = []
    for subtree in res.subtrees(filter=lambda t: t.node == 'PERSON'):
        subtree_l=[]
        for leaf in subtree.leaves():
            subtree_l.append(leaf[0])
        sub = ' '.join(subtree_l)
        tree.append(sub)

    for subtree in res.subtrees(filter=lambda t: t.node == 'ORGANIZATION'):
        subtree_l=[]
        for leaf in subtree.leaves():
            subtree_l.append(leaf[0])
        sub = ' '.join(subtree_l)
        tree.append(sub)
    x= ', '.join(tree)
    count = count+1
    print x