code: def init_col_filter(columns, source)
          if columns.nil?
            File.open(source, 'r').each do |line| 
              line = unstring(line)
              next if line.empty?
              line += ' ' if line =~ /;$/
              size = line.split(';').size
              columns = "0-#{size-1}"
              break
            end
          end
          ColumnFilter.new(columns).filter.flatten
        end
docs: Initialize the col_filter that contains columns to be considered for
   mapping. If no columns are provided, that is being empty, a filter with
   all columns is returned