code: public GitlabMergeRequest getMergeRequestByIid(Serializable projectId, Integer mergeRequestIid) throws IOException {
          String tailUrl = GitlabProject.URL + "/" + sanitizeProjectId(projectId) + GitlabMergeRequest.URL + "/" + mergeRequestIid;
          return retrieve().to(tailUrl, GitlabMergeRequest.class);
      }
docs: Return Merge Request.
  
  @param projectId       The id of the project
  @param mergeRequestIid The internal id of the merge request
  @return the Gitlab Merge Request
  @throws IOException on gitlab api call error