code: def formula_form_for(record_or_name_or_array, *args, &proc)
        options = args.extract_options!
        options[:builder] ||= @@builder
        form_for(record_or_name_or_array, *(args << options), &proc)
      end
docs: Generates a wrapper around form_for with :builder set to FormulaFormBuilder.
  
   Supports:
  
   * formula_form_for(@user)
  
   Equivalent:
  
   * form_for(@user, :builder => Formula::FormulaFormBuilder))
  
   Usage:
  
     <% formula_form_for(@user) do |f| %>
       <%= f.input :email %>
       <%= f.input :password %>
     <% end %>