code: def init_sum_scheme(sum_scheme)
  
          return if sum_scheme.nil?
  
          re = /(\w+):(\d+)|(\w+)/
  
          sum_scheme.scan(re).each do |part|
            if part.compact.size == 2
              @sum_row_title = part[0]
              @sum_row       = part[1].to_i
            else
              @sum_col_title = part[2]
            end
          end
  
        end
docs: Initializes the sum row title an positions as well as the sum column
   title