Obtaining Access Token for Keycloak User Using Admin Account

I have a Keycloak server for SSO. In this server, there may be many users. I need a way to obtain an access token for a specific user (for example, John in the realm ‘test_realm’) using an admin account from the master realm. I only have the user’s user ID or username and do not have the user’s password. I also use the python-keycloak Python library for communication with the Keycloak server(but it’s not important. If you have a solution for this using cURL, please let me know). How can I do that?

Version: 20.0.2
Product: Default
Admin UI version: 911eb6b83b301a990cbd0029c086150dfef279e9