code: def render_headers(self):
          
          lines = []
  
          sort_keys = ['Content-Disposition', 'Content-Type', 'Content-Location']
          for sort_key in sort_keys:
              if self.headers.get(sort_key, False):
                  lines.append('%s: %s' % (sort_key, self.headers[sort_key]))
  
          for header_name, header_value in self.headers.items():
              if header_name not in sort_keys:
                  if header_value:
                      lines.append('%s: %s' % (header_name, header_value))
  
          lines.append('\r\n')
          return '\r\n'.join(lines)
docs: Renders the headers for this request field.