code: import os
  
  import cassio
  import langchain
  from langchain.cache import CassandraCache
  from langchain_community.chat_models import ChatOpenAI
  from langchain_core.messages import BaseMessage
  from langchain_core.prompts import ChatPromptTemplate
  from langchain_core.runnables import RunnableLambda
  
  use_cassandra = int(os.environ.get("USE_CASSANDRA_CLUSTER", "0"))
  if use_cassandra:
      from .cassandra_cluster_init import get_cassandra_connection
  
      session, keyspace = get_cassandra_connection()
      cassio.init(
          session=session,
          keyspace=keyspace,
      )
  else:
      cassio.init(
          token=os.environ["ASTRA_DB_APPLICATION_TOKEN"],
          database_id=os.environ["ASTRA_DB_ID"],
          keyspace=os.environ.get("ASTRA_DB_KEYSPACE"),
      )
  
  # inits
  langchain.llm_cache = CassandraCache(session=None, keyspace=None)
  llm = ChatOpenAI()
  
  
  # custom runnables
  def msg_splitter(msg: BaseMessage):
      return [w.strip() for w in msg.content.split(",") if w.strip()]
  
  
  # synonym-route preparation
  synonym_prompt = ChatPromptTemplate.from_template(
      "List up to five comma-separated synonyms of this word: {word}"
  )
  
  chain = synonym_prompt | llm | RunnableLambda(msg_splitter)
  
apis: langchain_core.runnables.RunnableLambda langchain_core.prompts.ChatPromptTemplate.from_template langchain.cache.CassandraCache langchain_community.chat_models.ChatOpenAI
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