code: public MergeRequest createMergeRequest(Object projectIdOrPath, String sourceBranch, String targetBranch, String title, String description, Integer assigneeId)
              throws GitLabApiException {
          return createMergeRequest(projectIdOrPath, sourceBranch, targetBranch, title, description, assigneeId, null, null, null, null);
      }
docs: Creates a merge request and optionally assigns a reviewer to it.
  
  <pre><code>GitLab Endpoint: POST /projects/:id/merge_requests</code></pre>
  
  @param projectIdOrPath the project in the form of an Integer(ID), String(path), or Project instance
  @param sourceBranch the source branch, required
  @param targetBranch the target branch, required
  @param title the title for the merge request, required
  @param description the description of the merge request
  @param assigneeId the Assignee user ID, optional
  @return the created MergeRequest instance
  @throws GitLabApiException if any exception occurs