code: function(el, tagName, tagData){
  		var helperTagCallback = tagData.options.get('tags.' + tagName,{proxyMethods: false}),
  			tagCallback = helperTagCallback || tags[tagName];
  
  		// If this was an element like <foo-bar> that doesn't have a component, just render its content
  		var scope = tagData.scope,
  			res;
  			
  		if(tagCallback) {
  			res = can.__notObserve(tagCallback)(el, tagData);
  		} else {
  			res = scope;
  		}
  
  		//!steal-remove-start
  		if (!tagCallback) {
  			can.dev.warn('can/view/scanner.js: No custom element found for ' + tagName);
  		}
  		//!steal-remove-end
  
  		// If the tagCallback gave us something to render with, and there is content within that element
  		// render it!
  		if (res && tagData.subtemplate) {
  
  			if (scope !== res) {
  				scope = scope.add(res);
  			}
  			var result = tagData.subtemplate(scope, tagData.options);
  			var frag = typeof result === "string" ? can.view.frag(result) : result;
  			can.appendChild(el, frag);
  		}
  	}
docs: handles calling back a tag callback