code: public Epic updateEpic(Object groupIdOrPath, Integer epicIid, String title, String labels, String description,
              Date startDate, Date endDate) throws GitLabApiException {
          Form formData = new GitLabApiForm()
                  .withParam("title", title, true)
                  .withParam("labels", labels)
                  .withParam("description", description)
                  .withParam("start_date", startDate)
                  .withParam("end_date", endDate);
          Response response = put(Response.Status.OK, formData.asMap(),
                  "groups", getGroupIdOrPath(groupIdOrPath), "epics", epicIid);
          return (response.readEntity(Epic.class));
      }
docs: Updates an existing epic.
  
  <pre><code>GitLab Endpoint: PUT /groups/:id/epics/:epic_iid</code></pre>
  
  @param groupIdOrPath the group ID, path of the group, or a Group instance holding the group ID or path
  @param epicIid the IID of the epic to update
  @param title the title of the epic (optional)
  @param labels comma separated list of labels (optional)
  @param description the description of the epic (optional)
  @param startDate the start date of the epic (optional)
  @param endDate the end date of the epic (optional)
  @return an Epic instance containing info on the newly created epic
  @throws GitLabApiException if any exception occurs