code: def convert(self, request, response, data):
          
  
          # Determine which time to use
          fmtstr = self.modifier.param
          if fmtstr is None:
              log_time = data['start']
          elif fmtstr == 'begin' or fmtstr.startswith('begin:'):
              log_time = data['start']
              if fmtstr == 'begin':
                  fmtstr = None
              else:
                  fmtstr = fmtstr[len('begin:'):]
          elif fmtstr == 'end' or fmtstr.startswith('end:'):
              log_time = time.time()
              if fmtstr == 'end':
                  fmtstr = None
              else:
                  fmtstr = fmtstr[len('end:'):]
          else:
              log_time = data['start']
  
          # Next, determine the format to use
          if fmtstr is None:
              fmtstr = "[%d/%b/%Y:%H:%M:%S +0000]"
          elif fmtstr in ('sec', 'msec', 'usec', 'msec_frac', 'usec_frac'):
              mult = 1
              fld_len = 0
  
              # Handle microseconds and milliseconds
              if fmtstr.startswith('usec'):
                  mult = 1000000
                  fld_len = 6
              elif fmtstr.startswith('msec'):
                  mult = 1000
                  fld_len = 3
  
              # Adjust for request for fractions
              if fmtstr.endswith('_frac'):
                  log_time = int((log_time * mult) - (int(log_time) * mult))
              else:
                  log_time = int(log_time * mult)
                  fld_len = 0
  
              # Return the formatted result
              return "%0*d" % (fld_len, log_time)
  
          return time.strftime(fmtstr, time.gmtime(log_time))
docs: 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.