docs: def set_response_content_type(self):
          """Set the Content-Type in the response. Uses the :attr:`type`
          instance attribute which was set by :func:`get_content_type`. Also
          declares a UTF-8 charset.
          """
          if self.response.body:
              ct = self.type
              if self.charset:
                  ct += '; charset=' + self.charset
              self.response.headers['Content-Type'] = ct
          elif 'Content-Type' in self.response.headers:
              del self.response.headers['Content-Type']