ptree = ParentedTree.fromstring(
    '(ROOT (S (NP (JJ Congressional)     (NNS representatives)) (VP (VBP are) (VP (VBN motivated)     (PP (IN by) (NP (NP (ADJ shiny) (NNS money))))))) (. .))'
    )
NLTK tree data structure, finding a node, it's parent or children