def _table_columns(first_table_row):
    """Find column ranges in output line.

    Return list of tuples (start,end) for each column
    detected by plus (+) characters in delimiter line.
    """
    positions = []
    start = 1
    while start < len(first_table_row):
        end = first_table_row.find('+', start)
        if end == -1:
            break
        positions.append((start, end))
        start = end + 1
    return positions
