How are there no videos of cops arresting other cops

Is it in their training, or are they legally not allowed to arrest other cops? Note that i mean a cop arresting another cop in uniform/while on duty. Im just flabbergasted that cops, once in uniform, are somehow entirely exempt from law enforcement themselves as anything they ever do wrong is only identified by a post-event internal investigation (at most). So it seems that no cop is ever ever ever willing to immediately arrest/stop/interfere with another cop while theyre in uniform.