presto-google-sheets/src/main/java/io/prestosql/plugin/google/sheets/SheetsClient.java/SheetsClient/getAllTableSheetExpressionMapping
class SheetsClient:    private Map<String, Optional<String>> getAllTableSheetExpressionMapping()
    {
        ImmutableMap.Builder<String, Optional<String>> tableSheetMap = ImmutableMap.builder();
        List<List<Object>> data = readAllValuesFromSheetExpression(metadataSheetId);
        // first line is assumed to be sheet header
        for (int i = 1; i < data.size(); i++) {
            if (data.get(i).size() >= 2) {
                String tableId = String.valueOf(data.get(i).get(0));
                String sheetId = String.valueOf(data.get(i).get(1));
                tableSheetMap.put(tableId.toLowerCase(Locale.ENGLISH), Optional.of(sheetId));
            }
        }
        return tableSheetMap.build();
    }