Initialize self. See help(type(self)) for accurate signature.
If key is not found, d is returned if given, otherwise KeyError is raised.
as a 2-tuple; but raise KeyError if D is empty.
If E present and has a .keys() method, does: for k in E: D[k] = E[k] If E present and lacks .keys() method, does: for (k, v) in E: D[k] = v In either case, this is followed by: for k, v in F.items(): D[k] = v