presto-google-sheets/src/main/java/io/prestosql/plugin/google/sheets/SheetsMetadata.java/SheetsMetadata/getColumnHandles
class SheetsMetadata:    @Override
    public Map<String, ColumnHandle> getColumnHandles(ConnectorSession session, ConnectorTableHandle tableHandle)
    {
        SheetsTableHandle sheetsTableHandle = (SheetsTableHandle) tableHandle;
        Optional<SheetsTable> table = sheetsClient.getTable(sheetsTableHandle.getTableName());
        if (!table.isPresent()) {
            throw new TableNotFoundException(sheetsTableHandle.toSchemaTableName());
        }

        ImmutableMap.Builder<String, ColumnHandle> columnHandles = ImmutableMap.builder();
        int index = 0;
        for (ColumnMetadata column : table.get().getColumnsMetadata()) {
            columnHandles.put(column.getName(), new SheetsColumnHandle(column.getName(), column.getType(), index));
            index++;
        }
        return columnHandles.build();
    }