def init_collection(column_filter)
        column_filter.split('+').each do |f|
          category, filter = f.split(':')
          collection[category] = { entries: [], filter: ColumnFilter.new(filter) }
        end 
      end
def init_collection(column_filter)
        column_filter.split('+').each do |f|
          category, filter = f.split(':')
          collection[category] = { entries: [], filter: ColumnFilter.new(filter) }
        end 
      end
Initializes the collection