why checkbox, list of collection dosen't work in rails 5

I want to choose from a collection, i tried the code below, but it render only the values and the levels of AttributeType not the collection of check_boxes containing these values.

my form_file:

 <%= simple_form_for @rule do |f| %>


      <%= f.input :id  ,class:"form-control form-control-lg",placeholder: 'The id of your rule' %>

      <p class="control">
      <%= f.collection_check_boxes :at_suj, AttributeType.all, :value, :level do |m| %>
        <%= m.label class: 'checkbox' do %>
          <%= m.check_box class: 'checkbox' %>
          <%= m.text %>

          <% end %>
          <% end %>
        </p>
      </div>
  <div class="actions"> 
    <%= f.button :submit, class:"btn btn-success btn-rounded ",title:"cliquer pour créer cette règle" %>
    <% end %>

where is the problem!