从内存中删除lxml对象？

Question

我正在尝试从内存中删除一个巨大的lxml对象。 我试过close（）方法但是tree.close（）给我一个错误信息（它说树对象没有这个方法）。有人知道一个好技术吗？

    from lxml import etree as ET
    import gc
    path  = # insert a big xml path and filename here
    tree = ET.parse(path)
    # --- Here I use data in some way ---
    # now I don't use that tree anymore
    del tree
    gc.collect()
    # after this, data still in memory