def __init__(self, *args, **kwds):
            if len(args) > 1:
                raise TypeError('expected at most 1 arguments, got %d' % len(args))
            try:
                self.__root
            except AttributeError:
                self.__root = root = []                     # sentinel node
                root[:] = [root, root, None]
                self.__map = {}
            self.__update(*args, **kwds)
Initialize an ordered dictionary.  Signature is the same as for
dataset/ETHPy150Open xraypy/xraylarch/doc/sphinx/ext/backports.py/OrderedDict.__init__