instance method attachment

# File actionmailer/lib/action_mailer/vendor/tmail-1.2.7/tmail/attachments.rb, line 45
    def attachment(part)
      if part.multipart?
        part.attachments
      elsif attachment?(part)
        content   = part.body # unquoted automatically by TMail#body
        file_name = (part['content-location'] && part['content-location'].body) ||
                    part.sub_header('content-type', 'name') ||
                    part.sub_header('content-disposition', 'filename') ||
                    'noname'

        return if content.blank?

        attachment = TMail::Attachment.new(content)
        attachment.original_filename = file_name.strip unless file_name.blank?
        attachment.content_type = part.content_type
        attachment
      end
    end