def METHOD_NAME(cls, serviceInfoDict):
    """initialize handler"""
    log = LOG.getSubLogger("initializeHandler")
    for seName in DMSHelpers().getStorageElements():
        se = StorageElement(seName)
        # TODO: once we finally merge _allProtocolParameters with the
        # standard paramaters in the StorageBase, this will be much neater
        for storagePlugin in se.storages.values():
            storageParam = storagePlugin._allProtocolParameters  # pylint: disable=protected-access
            if (
                storageParam.get("Protocol") == "s3"
                and "Aws_access_key_id" in storageParam
                and "Aws_secret_access_key" in storageParam
            ):
                cls._S3Storages[seName] = storagePlugin
                log.debug(f"Add {seName} to the list of usable S3 storages")
                break
    log.info("S3Gateway initialized storages", f"{list(cls._S3Storages)}")
    cls._fc = FileCatalog()
    return S_OK()