def convert(self, request, response, data):
        """
        Performs the desired Conversion.

        :param request: The webob Request object describing the
                        request.
        :param response: The webob Response object describing the
                         response.
        :param data: The data dictionary returned by the prepare()
                     method.

        :returns: A string, the results of which are the desired
                  conversion.
        """

        size = response.content_length
        if not size:
            size = "-" if self.conv_chr == 'b' else 0

        return str(size)
Performs the desired Conversion.

        :param request: The webob Request object describing the
                        request.
        :param response: The webob Response object describing the
                         response.
        :param data: The data dictionary returned by the prepare()
                     method.

        :returns: A string, the results of which are the desired
                  conversion.