Can I add a deduction guide to `std` namespace?

Question

Suppose I want to make a new deduction guide making the following possible ?

std::string str;
std::basic_string_view sv = str;

Would that be an Ok customization ?

Answer 1

[namespace.std]/2.4:

The behavior of a C++ program is undefined if it declares [...] a deduction guide for any standard library class template.