'This method modifies the tree in three ways:
1. Transforms a tree in Chomsky Normal Form back to its
original structure (branching greater than two)
2. Removes any parent annotation (if it exists)
3. (optional) expands unary subtrees (if previously
collapsed with collapseUnary(...) )
:param expandUnary: Flag to expand unary or not (default = True)
:type  expandUnary: bool
:param childChar: A string separating the head node from its children in an artificial node (default = "|")
:type  childChar: str
:param parentChar: A sting separating the node label from its parent annotation (default = "^")
:type  parentChar: str
:param unaryChar: A string joining two non-terminals in a unary production (default = "+")
:type  unaryChar: str'

def un_chomsky_normal_form(self, expandUnary=True, childChar=u'|', parentChar=u'^', unaryChar=u'+'):

    from nltk.treetransforms import un_chomsky_normal_form
    un_chomsky_normal_form(self, expandUnary, childChar, parentChar, unaryChar)
