code: public void deleteVariable(Object groupIdOrPath, String key) throws GitLabApiException {
          delete(Response.Status.NO_CONTENT, null, "groups", getGroupIdOrPath(groupIdOrPath), "variables", key);
      }
docs: Deletes a group variable.
  
  <pre><code>DELETE /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, required
  @param key the key of an existing variable, required
  @throws GitLabApiException if any exception occurs