How to use the numexpr.expressions._context.set_new_context function in numexpr

elif name == "True":
                names[name] = True
            elif name == "False":
                names[name] = False
            else:
                t = types.get(name, default_type)
                names[name] = expressions.VariableNode(name, type_to_kind[t])
        names.update(expressions.functions)
        # now build the expression
        ex = eval(c, names)
        if expressions.isConstant(ex):
            ex = expressions.ConstantNode(ex, expressions.getKind(ex))
        elif not isinstance(ex, expressions.ExpressionNode):
            raise TypeError("unsupported expression type: %s" % type(ex))
    finally:
        expressions._context.set_new_context(old_ctx)
    return ex