<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def users(self):
 """ Returns known users by exposing as a read-only property. """

        if not hasattr(self, "_users"):
            us = {}
            if "users" in self.doc:
                for ur in self.doc["users"]:
                    us[ur["name"]] = u = copy.deepcopy(ur["user"])
                    BytesOrFile.maybe_set(u, "client-certificate")
                    BytesOrFile.maybe_set(u, "client-key")
            self._users = us
        return self._users