Make object_id mandatory in save_synonym

algoliasearch/index.py

@@ -543,13 +543,13 @@ def browse_all(self, params=None):
         """
         return IndexIterator(self, params=params)
 
-    def save_synonym(self, content, object_id='', forward_to_slaves=False):
+    def save_synonym(self, content, object_id, forward_to_slaves=False):
         """
         Add a synonym in this index.
 
         @param content contains the synonyms set to add to the index.
             The object is represented by an associative array
-        @param object_id (optional) unique identifier for the new synonym.
+        @param object_id unique identifier for the new synonym.
             If the identifier already exists, the old synonym is replaced
         @param forward_to_slaves (optional) should the changes be forwarded to
             slave indexes