code: function(ast) {
        var detected = [];
  
        ast.traverseByTypes(['block', 'value'], function(block, i, parent) {
          if (block.is('value') && !block.first().is('block')) return;
  
          var previousNode = parent.get(i - 1);
          if (!previousNode) return;
  
          // If it's spaces, modify this node.
          // If it's something different from spaces, add a space node to
          // the end:
          if (previousNode.is('space')) {
            detected.push(previousNode.content);
          } else {
            detected.push('');
          }
        });
  
        return detected;
      }
docs: Detects the value of an option at the tree node.
  
  @param {node} ast