code: def lookup(self, token):
      
      # get search key and env/service from token
      try:
        key, envservice = token.split(",")
      except ValueError:
        return None
      # get env, service from value
      try:
        env, service = envservice.split("/")
      except ValueError as e:
        raise RuntimeError("Request:{} can't resolve to env, service. {}".format(envservice, e.message))
  
      return self._s3_get(env, service, key)
docs: Return key version if found, None otherwise
      Lookup should look like this:
        pattern:
        <key>,<env>/<service>
        example:
        ami-id,staging/core