Allow more subclassing of self-chat world

parlai/tasks/self_chat/worlds.py

@@ -132,13 +132,7 @@ def make_agent_action(utterance: str, agent: Agent) -> Dict[str, Any]:
 
     def parley(self):
         if self.episode_done():
-            self.turn_cnt = 0
-            self.episode_cnt += 1
-            self.contexts = None
-            self.seed_utterances = None
-            agents = self.get_agents()
-            for a in agents:
-                a.reset()
+            self._end_episode()
 
         if self.turn_cnt == 0:
             self.acts = [None, None]
@@ -160,7 +154,7 @@ def parley(self):
                 self.agents[i].observe(validate(context))
             # clear contexts so they are only added once per episode
             self.contexts = None
-        elif self.seed_utterances:
+        elif self.seed_utterances and self._use_seed_utterances():
             # pop the next two seed messages (there may be less or more than 2 total)
             utts = self.seed_utterances[:2]
             self.seed_utterances = self.seed_utterances[2:]
@@ -186,3 +180,24 @@ def parley(self):
 
         self.update_counters()
         self.turn_cnt += 1
+
+    def _end_episode(self):
+        """
+        Apply logic to end the episode.
+        """
+        self.turn_cnt = 0
+        self.episode_cnt += 1
+        self.contexts = None
+        self.seed_utterances = None
+        agents = self.get_agents()
+        for a in agents:
+            a.reset()
+
+    def _use_seed_utterances(self) -> bool:
+        """
+        Logic to determine whether we should employ seed utterances.
+
+        Defaults to always using seed utterances if they exist, but this can be
+        overridden.
+        """
+        return True