protected function _parseTableSizes($reset = false)
    {
        if ($reset) $this->_resetSizes();
        $this->line_size = count($this->tbody);
        foreach (self::$_table_parts as $part) {
            if (!empty($this->{$part}) && is_array($this->{$part})) {
                foreach ($this->{$part} as $part_line) {
                    $line_cells_count = 0;
                    foreach ($part_line as $part_cell) {
                        $line_length = strlen($part_cell)+2;
                        if ($line_length > $this->cell_size) {
                            $this->cell_size = $line_length;
                        }
                        $line_cells_count++;
                    }
                    if ($line_cells_count > $this->column_size) {
                        $this->column_size = $line_cells_count;
                    }
                }
            }
        }
    }