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 =~ /;$/
            size = line.split(';').size
            columns = "0-#{size-1}"
            break
          end
        end
        ColumnFilter.new(columns).filter.flatten
      end
def init_col_filter(columns, source)
        if columns.nil?
          File.open(source, 'r').each do |line| 
            line = unstring(line)
            next if line.empty?
            line += ' ' if line =~ /;$/
            size = line.split(';').size
            columns = "0-#{size-1}"
            break
          end
        end
        ColumnFilter.new(columns).filter.flatten
      end
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