Class Convert not found

<%- if @topic_view.topic.tags.present? %>
<%= t 'js.tagging.tags' %>: <%- @topic_view.topic.tags.each do |t| %> <%= t %> <%- end %>
<% end %>

Silverstripe Version: 4.1

Question:
Why class ‘Convert’ not found?

Details of your query go here

use SilverStripe\Core\Convert;

function my_function(){
	$pw = Convert::raw2sql($password);
}