def remove_builtin(self, key):
        try:
            orig = self._orig_builtins.pop(key)
        except KeyError:
            pass
        else:
            if orig is BuiltinUndefined:
                del builtins.__dict__[key]
            else:
                builtins.__dict__[key] = orig
Remove an added builtin and re-set the original.
dataset/ETHPy150Open ipython/ipython-py3k/IPython/core/builtin_trap.py/BuiltinTrap.remove_builtin