tree.search('001') returning nothing

[adiv5]

After doing the steps as mentioned, when i try to query a ICD9 code using script , i am not getting any results returned. Im importing ICD9 class in script , then making a tree object using codes.json, then doing tree.search('001') and its not returning anything.Not even for other codes.

However surprisingly,this works

    toplevelnodes = tree.children
    toplevelcodes = [node.code for node in toplevelnodes]
    print('\t'.join(toplevelcodes))

cant figure out how to deal with this. Thanks