RemixIconEx.System.arrow_up_down

You're seeing just the function arrow_up_down, go back to RemixIconEx.System module for more information.
Link to this function

arrow_up_down(icon_css_class \\ "icon")

iex> Elixir.RemixIconEx.System.arrow_up_down()
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" class="icon">
  <path d="M11.95 7.95l-1.414 1.414L8 6.828 8 20H6V6.828L3.465 9.364 2.05 7.95 7 3l4.95 4.95zm10 8.1L17 21l-4.95-4.95 1.414-1.414 2.537 2.536L16 4h2v13.172l2.536-2.536 1.414 1.414z" />
</svg>

example usage

svg.icon {
  width: 96;
  height: 96;
}