presto-hive/src/main/java/io/prestosql/plugin/hive/metastore/file/FileHiveMetastore.java/FileHiveMetastore/readRoleGrantsFile
class FileHiveMetastore:    private Set<RoleGrant> readRoleGrantsFile()
    {
        return ImmutableSet.copyOf(readFile("roleGrants", getRoleGrantsFile(), roleGrantsCodec).orElse(ImmutableList.of()));
    }