How to use the asteval.astutils.UNSAFE_ATTRS function in asteval

def on_attribute(self, node):    # ('value', 'attr', 'ctx')
        """Extract attribute."""
        ctx = node.ctx.__class__
        if ctx == ast.Store:
            msg = "attribute for storage: shouldn't be here!"
            self.raise_exception(node, exc=RuntimeError, msg=msg)

        sym = self.run(node.value)
        if ctx == ast.Del:
            return delattr(sym, node.attr)

        # ctx is ast.Load
        fmt = "cannnot access attribute '%s' for %s"
        if node.attr not in UNSAFE_ATTRS:
            fmt = "no attribute '%s' for %s"
            try:
                return getattr(sym, node.attr)
            except AttributeError:
                pass

        # AttributeError or accessed unsafe attribute
        obj = self.run(node.value)
        msg = fmt % (node.attr, obj)
        self.raise_exception(node, exc=AttributeError, msg=msg)