code: def header_echo(cls, request,
                      api_key: (Ptypes.header, String('API key'))) -> [
              (200, 'Ok', String)]:
          '''Echo the header parameter.'''
          log.info('Echoing header param, value is: {}'.format(api_key))
          for i in range(randint(0, MAX_LOOP_DURATION)):
              yield
          msg = 'The value sent was: {}'.format(api_key)
          Respond(200, msgf header_echo(cls, request,
                      api_key: (Ptypes.header, String('API key'))) -> [
              (200, 'Ok', String)]:
          '''Echo the header parameter.'''
          log.info('Echoing header param, value is: {}'.format(api_key))
          for i in range(randint(0, MAX_LOOP_DURATION)):
              yield
          msg = 'The value sent was: {}'.format(api_key)
          Respond(200, msg)
docs: Echo the header parameter.