presto-hive/src/main/java/io/prestosql/plugin/hive/metastore/thrift/ThriftHiveMetastore.java/ThriftHiveMetastore/grantRoles
class ThriftHiveMetastore:    @Override
    public void grantRoles(Set<String> roles, Set<HivePrincipal> grantees, boolean withAdminOption, HivePrincipal grantor)
    {
        for (HivePrincipal grantee : grantees) {
            for (String role : roles) {
                grantRole(
                        role,
                        grantee.getName(), fromPrestoPrincipalType(grantee.getType()),
                        grantor.getName(), fromPrestoPrincipalType(grantor.getType()),
                        withAdminOption);
            }
        }
    }