code: def _initialize_aws_identity_document(cls):
          
  
          if cls.inited:
              return
  
          content = get_request(_AWS_INSTANCE_IDENTITY_DOCUMENT_URI)
          if content is not None:
              content = json.loads(content)
              for env_var, attribute_key in _AWS_ATTRIBUTES.items():
                  attribute_value = content.get(env_var)
                  if attribute_value is not None:
                      aws_metadata_map[attribute_key] = attribute_value
  
              cls.is_running = True
  
          cls.inited = True
docs: This method, tries to establish an HTTP connection to AWS instance
          identity document url. If the application is running on an EC2
          instance, we should be able to get back a valid JSON document. Make a
          http get request call and store data in local map.
          This method should only be called once.