# File lib/amrita/template.rb, line 12
    def cache(filename, typ, source_mtime=nil, key=nil, &block)
      source_mtime = Time.new unless source_mtime
      item = get_item(typ, filename, key) || Item.new
      unless valid_item?(item, source_mtime)
        item.filename = filename
        item.type = typ
        item.key = key
        item.mtime = source_mtime
        item.contents = yield
        save_item(item)
      end
      item.contents
    end

# File lib/amrita/template.rb, line 26
    def valid_item?(item, source_mtime)
      item.mtime && source_mtime && item.mtime >= source_mtime
    end