anchor.diff:  
         <div class="panel-body">
           <%= f.field_container :categories, :class => ['form-group'] do %>
  -          <%= f.select :tax_category_id, @tax_categories.map { |tc| [tc.name, tc.id] }, {include_blank: true}, class: "select2" %>
  +          <%= f.select :tax_category_id, @tax_categories.map { |tc| [tc.name, tc.id] }, { include_blank: true }, class: "select2" %>
             <%= error_message_on :shipping_method, :tax_category_id %>
           <% end %>
         </div>
  
positive.code:     <div data-hook="admin_shipping_method_form_code" class="col-md-4">
        <%= f.field_container :code, :class => ['form-group'] do %>
          <%= f.label :code, Spree.t(:code) %>
          <%= f.text_field :code, :class => 'form-control', :label => false  %>
          <%= error_message_on :shipping_method, :code %>
        <% end %>
      </div>
  
negative.code:         <%= f.field_container :zones, :class => ['form-group'] do %>
            <% shipping_method_zones = @shipping_method.zones.to_a %>
            <% Spree::Zone.all.each do |zone| %>
              <div class="checkbox">
                <%= label_tag do %>
                  <%= check_box_tag('shipping_method[zones][]', zone.id, shipping_method_zones.include?(zone)) %>
                  <%= zone.name %>
                <% end %>
              </div>
            <% end %>
            <%= error_message_on :shipping_method, :zone_id %>
          <% end %>
        </div>
      </div>
    </div>
  