RemixIconEx.System.add_circle

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

add_circle(icon_css_class \\ "icon")

iex> Elixir.RemixIconEx.System.add_circle()
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" class="icon">
  <path d="M11 11V7h2v4h4v2h-4v4h-2v-4H7v-2h4zm1 11C6.477 22 2 17.523 2 12S6.477 2 12 2s10 4.477 10 10-4.477 10-10 10zm0-2a8 8 0 1 0 0-16 8 8 0 0 0 0 16z" />
</svg>

example usage

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