def issue_comments(self, issue_id_or_key, extra_query_params={}):
        """
        client = BacklogClient("your_space_name", "your_api_key")
        client.issue_comments("YOUR_PROJECT-999")
        """
        return self.do("GET", "issues/{issue_id_or_key}/comments",
                        url_params={"issue_id_or_key": issue_id_or_key},
                        query_params=extra_query_params
                        )
client = BacklogClient("your_space_name", "your_api_key")
        client.issue_comments("YOUR_PROJECT-999")