How can I get list of user from code and what’s the method that doing this and where I can found it??
Look here for the docs:
in your case, you would do
users = frappe.get_all("User")
users = frappe.get_list("User")
Look at the docs, there are many options you can add there.
Check also this recent thread, if you are looking for a particular value.
But it return empty list
frappe.db.get_list(doctype, filters, or_filters, fields, order_by, group_by, start, page_length)
or read it here: Hooks
did you try that in bench console?