presto-accumulo/src/main/java/io/prestosql/plugin/accumulo/conf/AccumuloTableProperties.java/AccumuloTableProperties/isExternal
class AccumuloTableProperties:    public static boolean isExternal(Map<String, Object> tableProperties)
    {
        requireNonNull(tableProperties);

        @SuppressWarnings("unchecked")
        Boolean serializerClass = (Boolean) tableProperties.get(EXTERNAL);
        return serializerClass;
    }