    # File lib/rack/multipart/generator.rb, line 12
          def dump
            return nil if @first && !multipart?
            return flattened_params if !@first

            flattened_params.map do |name, file|
              if file.respond_to?(:original_filename)
                ::File.open(file.path, "rb") do |f|
                  f.set_encoding(Encoding::BINARY) if f.respond_to?(:set_encoding)
                  content_for_tempfile(f, file, name)
                end
              else
                content_for_other(file, name)
              end
            end.join + "--#{MULTIPART_BOUNDARY}--\r"
          end