Fixed typo

wrappers/modelverse.py

@@ -72,7 +72,7 @@ def _get_metamodel(model):
     try:
         return registered_metamodels[model]
     except KeyError:
-        raise UnkownMetamodellingHierarchy(model)
+        raise UnknownMetamodellingHierarchy(model)
 
 def _check_type(value):
     if not isinstance(value, (int, long, float, str, unicode, bool)):