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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _get_checker(self, user):
 """ Return a ForumPermissionChecker instance for the given user. """

        user_perm_checkers_cache_key = user.id if not user.is_anonymous else 'anonymous'

        if user_perm_checkers_cache_key in self._user_perm_checkers_cache:
            return self._user_perm_checkers_cache[user_perm_checkers_cache_key]

        checker = ForumPermissionChecker(user)
        self._user_perm_checkers_cache[user_perm_checkers_cache_key] = checker
        return checker