'Return the token object from which this node was created.
Currently used only for printing an error message.
The error display routine in BaseRecognizer needs to
display where the input the error occurred. If your
tree of limitation does not store information that can
lead you to the token, you can create a token filled with
the appropriate information and pass that back.  See
BaseRecognizer.getErrorMessage().'

def getToken(self, t):

    raise NotImplementedError
