text: var walk = require('css-tree').walk;
  var handlers = {
      Atrule: require('./Atrule'),
      AttributeSelector: require('./AttributeSelector'),
      Value: require('./Value'),
      Dimension: require('./Dimension'),
      Percentage: require('./Percentage'),
      Number: require('./Number'),
      String: require('./String'),
      Url: require('./Url'),
      Hash: require('./color').compressHex,
      Identifier: require('./color').compressIdent,
      Function: require('./color').compressFunction
  };
  
  module.exports = function(ast) {
      walk(ast, {
          leave: function(node, item, list) {
              if (handlers.hasOwnProperty(node.type)) {
                  handlers[node.type].call(this, node, item, list);
              }
          }
      });
  };
  