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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def respond(self):
 """Process the current request. From :pep:`333`: The start_response callable must not actually transmit the response headers. Instead, it must store them for the server or gateway to transmit only after the first iteration of the application return value that yields a NON-EMPTY string, or upon the application's first invocation of the write() callable. """

        response = self.req.server.wsgi_app(self.env, self.start_response)
        try:
            for chunk in filter(None, response):
                if not isinstance(chunk, six.binary_type):
                    raise ValueError('WSGI Applications must yield bytes')
                self.write(chunk)
        finally:
            # Send headers if not already sent
            self.req.ensure_headers_sent()
            if hasattr(response, 'close'):
                response.close()