Convert multiple map values conditionally

Questions & Help Questions
,
1

I need to convert in place in a map some values only of they exist. The key can be either binary or atom.
Is there a more Elixir way to do it than my solution below?

 defp convert_time_params(params) do
    params
    |> (fn x ->
          if Map.has_key?(x, "start_time"), do: update_in(x, ["start_time"], &CalendarUtils.from_iso8601/1), else: x
        end).()
    |> (fn x ->
          if Map.has_key?(x, :start_time),
            do: update_in(x, [Access.key!(:start_time)], &CalendarUtils.from_iso8601/1),
            else: x
        end).()
    |> (fn x ->
          if Map.has_key?(x, "end_time"), do: update_in(x, ["end_time"], &CalendarUtils.from_iso8601/1), else: x
        end).()
    |> (fn x ->
          if Map.has_key?(x, :end_time),
            do: update_in(x, [Access.key!(:end_time)], &CalendarUtils.from_iso8601/1),
            else: x
        end).()
  end

The map is used in Ecto so I can not change the key type from atom to binary. I need to keep the input the same