code: public GitlabMergeRequest createMergeRequest(Serializable projectId, String sourceBranch, String targetBranch,
                                                   Integer assigneeId, String title) throws IOException {
  
          Query query = new Query()
                  .appendIf("target_branch", targetBranch)
                  .appendIf("source_branch", sourceBranch)
                  .appendIf("assignee_id", assigneeId)
                  .appendIf("title", title);
  
          String tailUrl = GitlabProject.URL + "/" + sanitizeProjectId(projectId) + GitlabMergeRequest.URL + query.toString();
  
          return dispatch().to(tailUrl, GitlabMergeRequest.class);
      }
docs: Create a new MergeRequest
  
  @param projectId
  @param sourceBranch
  @param targetBranch
  @param assigneeId
  @param title
  @return GitlabMergeRequest
  @throws IOException on gitlab api call error