GenServer in Elixir Server Callbacks

server_callbacks.exs

def handle_call({:unlock, password}, _from, passwords) do # ----> synchronous request
    if password in passwords do
      {:reply, :ok, passwords}

    else
     write_to_logfile password
    {:reply, {:error,"wrongpassword"}, passwords}
    end
end

def handle_call({:reset, {old_password,new_password}}, _from, passwords) do
    if old_password in passwords do
      new_state = List.delete(passwords,old_password)
      {:reply, :ok, [new_password | new_state]}
    else
      write_to_logfile new_password
    {:reply, {:error,"wrongpassword"}, passwords}

    end
end