def add_builtin(self, key, value):
        bdict = builtins.__dict__
        orig = bdict.get(key, BuiltinUndefined)
        if value is HideBuiltin:
            if orig is not BuiltinUndefined: #same as 'key in bdict'
                self._orig_builtins[key] = orig
                del bdict[key]
        else:
            self._orig_builtins[key] = orig
            bdict[key] = value
Add a builtin and save the original.
dataset/ETHPy150Open ipython/ipython-py3k/IPython/core/builtin_trap.py/BuiltinTrap.add_builtin