[schema] Add import to avoid deprecation warnings

schema.py

@@ -17,7 +17,8 @@
 
 """cubicweb-clinipath schema"""
 
-from yams.buildobjs import (EntityType, SubjectRelation, String, RichString, Int, Date)
+from yams.buildobjs import (String, RichString, Int, Date, Datetime,
+                            Float, Boolean, EntityType, SubjectRelation)
 
 
 class Biopsy(EntityType):