code: def add_to_sum_row(value, column)
          return unless @sum_row_patterns
          @sum_row_patterns.each do |pattern|
            if pattern =~ /^\(?c\d+[=~+.]/
              header_column = evaluate(pattern, "")
            else
              header_column = pattern
            end
  
            if header_column == column
              @sum_row[header_column] ||= 0
              @sum_row[header_column] += value
            end
          end
        end
docs: Adds a value in the specified column to the sum_row