1. On Tab1, from PurchaseSupply_view, click on 'Purchase Supply Lines':
   Base_viewListMode??proxy_form_id=PurchaseSupply_view&proxy_field_id=listbox

   This Python Script initialise 'list_mode_proxy_selection' with the
   above 2 GET parameters and then displays PurchaseSupply_view.listbox
   indirectly but current Form is Base_viewListModeRenderer.

2. On Tab2, from SaleSupply_view, click on 'Sale Supply Lines':
   Base_viewListMode?proxy_form_id=SaleSupply_view&proxy_field_id=listbox

   This Python Script initialise 'list_mode_proxy_selection' with the
   above 2 GET parameters and then displays SaleSupply_view.listbox
   indirectly but current Form is Base_viewListModeRenderer.

3. On Tab1, filter Purchase Supply Lines.

   As proxy_form_id and proxy_field_id are not given, then
   Base_viewListModeRender fallbacks on 'list_mode_proxy_selection'
   values to find out the Form ID to be called and wrongly display
   SaleSupply_view.listbox (2.).