docs: def write(self, chunk):
          """WSGI callable to write unbuffered data to the client.
          
          This method is also used internally by start_response (to write
          data from the iterable returned by the WSGI application).
          """
          if not self.started_response:
              raise AssertionError("WSGI write called before start_response.")
          
          if not self.req.sent_headers:
              self.req.sent_headers = True
              self.req.send_headers()
          
          self.req.write(chunk)