async function readAll() {
  try {
    const request = k8sModel.getClient('/api/v1/namespaces');
    const response = await request.get(`${GROUP_NAMESPACE}/secrets`, {
      headers: {
        Accept: 'application/json',
      },
    });
    const allGroupInstance = [];
    const groupData = response.data;
    for (const item of groupData.items) {
      try {
        const groupInstance = Group.createGroup({
          groupname: Buffer.from(item.data.groupname, 'base64').toString(),
          description: Buffer.from(item.data.description, 'base64').toString(),
          externalName: Buffer.from(
            item.data.externalName,
            'base64',
          ).toString(),
          extension: JSON.parse(
            Buffer.from(item.data.extension, 'base64').toString(),
          ),
        });
        allGroupInstance.push(groupInstance);
      } catch (error) {
        logger.debug(
          `secret ${item.metadata.name} is filtered in ${GROUP_NAMESPACE} due to group schema`,
        );
      }
    }
    return allGroupInstance;
  } catch (error) {
    if (error.response) {
      throw error.response;
    } else {
      throw error;
    }
  }
}
@function readAll - return all Groups' info.
@async
@return {Promise<Group[]>} A promise to all Group instance list.