-.. c:function:: memcached_return_t memcached_delete_by_key (memcached_st *ptr, const char *group_key, size_t group_key_length, const char *key, size_t key_length, time_t expiration);
+.. c:function:: memcached_return_t memcached_delete_by_key (memcached_st *ptr, const char *group_key, size_t group_key_length, const char *key, size_t key_length, time_t expiration)