rename alias to get slug aliases

tracim/lib/core/content.py

             # INFO - G.M - 2018-07-05 - convert with
             #  content type object to support legacy slug
             content_type_object = ContentType(content_type)
-            resultset = resultset.filter(Content.type.in_(content_type_object.alias()))
+            resultset = resultset.filter(Content.type.in_(content_type_object.get_slug_aliases()))
 
         if parent_id:
             resultset = resultset.filter(Content.parent_id==parent_id)

tracim/models/contents.py

                 return
         raise ContentTypeNotExist()
 
-    def alias(self) -> typing.List[str]:
-        """ Get all alias of a content, useful for legacy code convertion"""
+    def get_slug_aliases(self) -> typing.List[str]:
+        """
+        Get all slug aliases of a content,
+        useful for legacy code convertion
+        """
         # TODO - G.M - 2018-07-05 - Remove this legacy compat code
         # when possible.
         page_alias = [self.Page, self.PageLegacy]