code: function(model, callback) {
  			var self = this;
  			model.getRoot(function(root) {
  				// Find the existing ID reversely
  				var location = self.location;
  				while (location.length > 0) {
  					// Create a fake item
  					// NOTE: it's a hack because we don't have any efficient
  					//       way to get the actual file node. Instead, we have
  					//       to do it recursively starting from the root. If
  					//       you find anything wierd happens, change it to the
  					//       actual item object.
  					var item = {
  						Location: location
  					};
  					var id = model.getId(item);
  					// Test if this element exists
  					var exists = !!document.getElementById(id);
  					if (exists) {
  						callback(id);
  						return;
  					}
  					// Not found. This probably means this item is collapsed.
  					// Try to find one level upper.
  					// Here I assume every url starts from "/"
  					location = location.substr(0, location.lastIndexOf('/'));
  				}
  				// Nothing found
  				callback('');
  			});
  		}
docs: Find the deepest expanded folder item that contains the file having
  this annotation.
  
  @see IAnnotation for details.
  
  @param {orion.explorer.ExplorerModel} model -
  @param {Function} callback -