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Assigning additional values to an input

While the RunnableLambda function returns a single value, you will also need to preserve the current state. RunnablePassthrough does this by appending new keys to a dictionary holding the user input, so the inputs and results from RunnableLambda can be stored alongside one another.

Complete the code to add an additional output key to the chain's input.

This exercise is part of the course

Graph RAG with LangChain and Neo4j

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Exercise instructions

  • Use the correct runnable class to append an output key to the chain's input.
  • Extract the correct key from the input to multiply by 2 to complete the lambda function.

Hands-on interactive exercise

Have a go at this exercise by completing this sample code.

# Add an output key to the chain
chain = RunnablePassthrough.____(
  	# Multiply the input by 2
    output=lambda x: x[____] * 2
)

output = chain.invoke({"input": 2})
print(output)
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