code: def hello(environ, start_response):
      '''The WSGI_ application handler which returns an iterable
      over the "Hello World!" message.'''
      if environ['REQUEST_METHOD'] == 'GET':
          data = b'Hello World!\n'
          status = '200 OK'
          response_headers = [
              ('Content-type', 'text/plain'),
              ('Content-Length', str(len(data)))
          ]
          start_response(status, response_headers)
          return iter([data])
      else:
          raise MethodNotAllowef hello(environ, start_response):
      '''The WSGI_ application handler which returns an iterable
      over the "Hello World!" message.'''
      if environ['REQUEST_METHOD'] == 'GET':
          data = b'Hello World!\n'
          status = '200 OK'
          response_headers = [
              ('Content-type', 'text/plain'),
              ('Content-Length', str(len(data)))
          ]
          start_response(status, response_headers)
          return iter([data])
      else:
          raise MethodNotAllowed
docs: The WSGI_ application handler which returns an iterable
      over the "Hello World!" message.