code: public Variable getVariable(Object groupIdOrPath, String key) throws GitLabApiException {
        Response response = get(Response.Status.OK, null, "groups", getGroupIdOrPath(groupIdOrPath), "variables", key);
        return (response.readEntity(Variable.class));
      }
docs: Get the details of a group variable.
  
  <pre><code>GitLab Endpoint: GET /groups/:id/variables/:key</code></pre>
  
  @param groupIdOrPath the group ID, path of the group, or a Group instance holding the group ID or path
  @param key the key of an existing variable, required
  @return the Variable instance for the specified group variable
  @throws GitLabApiException if any exception occurs