'Set the node label of the tree.
>>> t = Tree.fromstring("(S (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))")
>>> t.set_label("T")
>>> print(t)
(T (NP (D the) (N dog)) (VP (V chased) (NP (D the) (N cat))))
:param label: the node label (typically a string)
:type label: any'

def set_label(self, label):

    self._label = label
