Output parsing variation allowance (langchain-ai#5178)

# Output parsing variation allowance for self-ask with search

This change makes self-ask with search easier for Llama models to
follow, as they tend toward returning 'Followup:' instead of 'Follow
up:' despite an otherwise valid remaining output.


Co-authored-by: Dev 2049 <dev.dev2049@gmail.com>

langchain/agents/self_ask_with_search/output_parser.py

@@ -1,24 +1,21 @@
-from typing import Union
+from typing import Sequence, Union
 
 from langchain.agents.agent import AgentOutputParser
 from langchain.schema import AgentAction, AgentFinish, OutputParserException
 
 
 class SelfAskOutputParser(AgentOutputParser):
+    followups: Sequence[str] = ("Follow up:", "Followup:")
+    finish_string: str = "So the final answer is: "
+
     def parse(self, text: str) -> Union[AgentAction, AgentFinish]:
-        followup = "Follow up:"
         last_line = text.split("\n")[-1]
-
-        if followup not in last_line:
-            finish_string = "So the final answer is: "
-            if finish_string not in last_line:
+        if not any([follow in last_line for follow in self.followups]):
+            if self.finish_string not in last_line:
                 raise OutputParserException(f"Could not parse output: {text}")
-            return AgentFinish({"output": last_line[len(finish_string) :]}, text)
-
-        after_colon = text.split(":")[-1]
+            return AgentFinish({"output": last_line[len(self.finish_string) :]}, text)
 
-        if " " == after_colon[0]:
-            after_colon = after_colon[1:]
+        after_colon = text.split(":")[-1].strip()
         return AgentAction("Intermediate Answer", after_colon, text)
 
     @property