code: def _consumers(self):
          
          consumers = {}
          for env in os.environ:
              if env.startswith('CONSUMER_KEY_SECRET_'):
                  key = env[20:]  # Strip off the CONSUMER_KEY_SECRET_ prefix
                  # TODO: remove below after live test
                  # consumers[key] = {"secret": os.environ[env], "cert": 'NA'}
                  consumers[key] = {"secret": os.environ[env], "cert": None}
          if not consumers:
              raise LTIException("No consumers found. Chalice stores "
                                 "consumers in Lambda environment variables. "
                                 "Have you created the environment variables?")
          return consumers
docs: Gets consumers from Lambda environment variables prefixed with
          CONSUMER_KEY_SECRET_. For example, given a consumer key of foo
          and a shared secret of bar, you should have an environment
          variable CONSUMER_KEY_SECRET_foo=bar.
  
          :return: consumers map
          :raises: LTIException if environment variables are not found