add all models as fallbacks (langchain-ai#290)

Author: baskaryan

backend/chain.py

@@ -236,39 +236,42 @@ def cohere_response_synthesizer(input: dict) -> RunnableSequence:
     )
 
 
-llm = ChatOpenAI(
-    model="gpt-3.5-turbo-0125",
+gpt_3_5 = ChatOpenAI(model="gpt-3.5-turbo-0125", temperature=0, streaming=True)
+claude_3_sonnet = ChatAnthropic(
+    model="claude-3-sonnet-20240229",
     temperature=0,
-    streaming=True,
-).configurable_alternatives(
+    max_tokens=4096,
+    anthropic_api_key=os.environ.get("ANTHROPIC_API_KEY", "not_provided"),
+)
+fireworks_mixtral = ChatFireworks(
+    model="accounts/fireworks/models/mixtral-8x7b-instruct",
+    temperature=0,
+    max_tokens=16384,
+    fireworks_api_key=os.environ.get("FIREWORKS_API_KEY", "not_provided"),
+)
+gemini_pro = ChatGoogleGenerativeAI(
+    model="gemini-pro",
+    temperature=0,
+    max_tokens=16384,
+    convert_system_message_to_human=True,
+    google_api_key=os.environ.get("GOOGLE_API_KEY", "not_provided"),
+)
+cohere_command = ChatCohere(
+    model="command",
+    temperature=0,
+    cohere_api_key=os.environ.get("COHERE_API_KEY", "not_provided"),
+)
+llm = gpt_3_5.configurable_alternatives(
     # This gives this field an id
     # When configuring the end runnable, we can then use this id to configure this field
     ConfigurableField(id="llm"),
     default_key="openai_gpt_3_5_turbo",
-    anthropic_claude_3_sonnet=ChatAnthropic(
-        model="claude-3-sonnet-20240229",
-        temperature=0,
-        max_tokens=4096,
-        anthropic_api_key=os.environ.get("ANTHROPIC_API_KEY", "not_provided"),
-    ),
-    fireworks_mixtral=ChatFireworks(
-        model="accounts/fireworks/models/mixtral-8x7b-instruct",
-        temperature=0,
-        max_tokens=16384,
-        fireworks_api_key=os.environ.get("FIREWORKS_API_KEY", "not_provided"),
-    ),
-    google_gemini_pro=ChatGoogleGenerativeAI(
-        model="gemini-pro",
-        temperature=0,
-        max_tokens=16384,
-        convert_system_message_to_human=True,
-        google_api_key=os.environ.get("GOOGLE_API_KEY", "not_provided"),
-    ),
-    cohere_command=ChatCohere(
-        model="command",
-        temperature=0,
-        cohere_api_key=os.environ.get("COHERE_API_KEY", "not_provided"),
-    ),
+    anthropic_claude_3_sonnet=claude_3_sonnet,
+    fireworks_mixtral=fireworks_mixtral,
+    google_gemini_pro=gemini_pro,
+    cohere_command=cohere_command,
+).with_fallbacks(
+    [gpt_3_5, claude_3_sonnet, fireworks_mixtral, gemini_pro, cohere_command]
 )
 
 retriever = get_retriever()