code: def render(self, f_buf=None):
          
          if f_buf is None:
              f_buf = StringIO.StringIO()
  
          headers = getattr(self, 'headers', ())
  
          keys = [
              force_encoding(header['label'], self.encoding)
              for header in headers
          ]
  
          extra_headers = getattr(self, 'extra_headers', ())
          keys.extend([
              force_encoding(header['label'], self.encoding)
              for header in extra_headers
          ])
  
          outfile = csv.DictWriter(
              f_buf,
              keys,
              extrasaction='ignore',
              delimiter=self.delimiter,
              quotechar=self.quotechar,
              quoting=csv.QUOTE_ALL,
          )
          outfile.writeheader()
          _datas = getattr(self, '_datas', ())
          outfile.writerows(_datas)
          f_buf.seek(0)
          return f_buf
docs: Write to the dest buffer
  
          :param obj f_buf: A file buffer supporting the write and seek
          methods