code: public void deleteMergedBranches(Object projectIdOrPath) throws GitLabApiException {
          delete(Response.Status.NO_CONTENT, null, "projects",
                  getProjectIdOrPath(projectIdOrPath), "repository", "merged_branches");
      }
docs: <p>Delete all branches that are merged into the project’s default branch.</p>
  NOTE: Protected branches will not be deleted as part of this operation.
  
  <pre><code>GitLab Endpoint: /projects/:id/repository/merged_branches</code></pre>
  
  @param projectIdOrPath the project in the form of an Integer(ID), String(path), or Project instance
  @throws GitLabApiException if any exception occurs