RemixIconEx.System.filter_3

You're seeing just the function filter_3, go back to RemixIconEx.System module for more information.
Link to this function

filter_3(icon_css_class \\ "icon")

iex> Elixir.RemixIconEx.System.filter_3()
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" class="icon">
  <path d="M10 18h4v-2h-4v2zM3 6v2h18V6H3zm3 7h12v-2H6v2z" />
</svg>

example usage

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