Custom admin URL

I tried this https://pimcore.com/docs/6.x/Development_Documentation/Development_Tools_and_Details/Custom_Admin_Login_Entry_Point.html

Output:

The configuration key “path” is unsupported for definition “my_custom_admin_entry_point” in “/var/www/projectname/htdocs/app/config/services.yml”. Allowed configuration keys are “alias”, “parent”, “class”, “shared”, “synthetic”, “lazy”,
“public”, “abstract”, “deprecated”, “factory”, “file”, “arguments”, “properties”, “configurator”, “calls”, “tags”, “decorates”, “decoration_inner_name”, “decoration_priority”, “autowire”, “autoconfigure”, “bind” in /var/www/projectname/h
tdocs/app/config/services.yml (which is being imported from “/var/www/projectname/htdocs/app/config/config.yml”).