Convert the top-level 'secrets' directive to the Docker format
        :return: secrets dict

def _get_top_level_secrets(self):
        """
        Convert the top-level 'secrets' directive to the Docker format
        :return: secrets dict
        """
        top_level_secrets = dict()
        if self.secrets:
            for secret, secret_definition in iteritems(self.secrets):
                if isinstance(secret_definition, dict):
                    for key, value in iteritems(secret_definition):
                        name = '{}_{}'.format(secret, key)
                        top_level_secrets[name] = dict(external=True)
                elif isinstance(secret_definition, string_types):
                    top_level_secrets[secret] = dict(external=True)
        return top_level_secrets