264        """
265        return not (attr.startswith("_") or is_internal_attribute(obj, attr))
266
267    def is_safe_callable(self, obj: t.Any) -> bool:268        """Check if an object is safely callable. By default callables
269        are considered safe unless decorated with :func:`unsafe`.
270

255        self.binop_table = self.default_binop_table.copy()
256        self.unop_table = self.default_unop_table.copy()
257
258    def is_safe_attribute(self, obj: t.Any, attr: str, value: t.Any) -> bool:259        """The sandboxed environment will call this method to check if the
260        attribute of an object is safe to access.  Per default all attributes
261        starting with an underscore are considered private as well as the

 467
 468    abstract = True
 469
 470    def as_const(self, eval_ctx: t.Optional[EvalContext] = None) -> t.Any: 471        """Return the value of the expression as constant or raise
 472        :exc:`Impossible` if this was not possible.
 473

 480        """
 481        raise Impossible()
 482
 483    def can_assign(self) -> bool: 484        """Check if it's possible to assign something to this node."""
 485        return False
 486

 53    def _default_finalize(value: t.Any) -> t.Any:
 54        return value
 55
 56    def _output_const_repr(self, group: t.Iterable[t.Any]) -> str: 57        return repr("".join([str(v) for v in group]))
 58
 59    def _output_child_to_const(