n success or olm_error() on failure. On failure last_error will be set with an error code. The last_error will be: * OUTPUT_BUFFER_TOO_SMALL if the buffer was too small * OLM_UNKNOWN_MESSAGE_INDEX if we do not have a session key corresponding to the given index (ie, it was sent before the session key was shared with us)</p></dd></dl><dl><dt class="spec value" id="val-outbound_group_session_size"><a href="#val-outbound_group_session_size" class="anchor"></a><code><span class="keyword">val</span> outbound_gro