Tree builders now advertise their features.

1 files changed, 10 insertions, 1 deletions

diff --git a/beautifulsoup/builder/_lxml.py b/beautifulsoup/builder/_lxml.py
index c2f368c..f5cc242 100644
--- a/beautifulsoup/builder/_lxml.py
+++ b/beautifulsoup/builder/_lxml.py
@@ -5,13 +5,20 @@ __all__ = [
 
 from lxml import etree
 from beautifulsoup.element import Comment, Doctype
-from beautifulsoup.builder import TreeBuilder, HTMLTreeBuilder
+from beautifulsoup.builder import (
+    FAST,
+    HTML,
+    HTMLTreeBuilder,
+    TreeBuilder,
+    XML)
 from beautifulsoup.dammit import UnicodeDammit
 import types
 
 class LXMLTreeBuilderForXML(TreeBuilder):
     DEFAULT_PARSER_CLASS = etree.XMLParser
 
+    features = [FAST, XML]
+
     @property
     def default_parser(self):
         # This can either return a parser object or a class, which
@@ -79,6 +86,8 @@ class LXMLTreeBuilderForXML(TreeBuilder):
 
 class LXMLTreeBuilder(HTMLTreeBuilder, LXMLTreeBuilderForXML):
 
+    features = [FAST, HTML]
+
     @property
     def default_parser(self):
         return etree.HTMLParser