Memory leak when using py7zlib to open .7z archives

Question

I am trying to use py7zlib to open and read files stored in .7z archives. I am able to do this, but it appears to be causing a memory leak. After scanning through a few hundred .7z files using py7zlib, Python crashes with a MemoryError. I don't have this problem when doing the equivalent operations on .zip files using the built-in zipfile library. My process with the .7z files is essentially as follows (look for a subfile in the archive with a given name and return its contents):

with open(filename, 'rb') as f:
    z = py7zlib.Archive7z(f)
    names = z.getnames()
    if subName in names:
        subFile = z.getmember(subName)
        contents = subFile.read()
    else:
        contents = None

return contents

Does anyone know why this would be causing a memory leak once the Archive7z object passes out of scope if I am closing the .7z file object? Is there any kind of cleanup or file-closing procedure I need to follow (like with the zipfile library's ZipFile.close())?