# File lib/mongo_mapper/plugins/associations/belongs_to_proxy.rb, line 6
        def replace(doc)
          if doc
            doc.save if !doc.persisted?
            id = doc.id
          end

          reset
          proxy_owner[association.foreign_key] = id
          unless doc.nil?
            loaded
            @target = doc
          end
          @target
        end