As you start interacting with Neo4j, you must call the query() method on a Neo4jGraph instance.
It is best practice to create a single instance of the Neo4jGraph class for use across the application.
In this challenge, you must create an instance using the environment variables added to the .env.local file in the previous module.
src/modules/graph.ts →
Create a Neo4jGraph instance
The src/modules/graph.ts file already has a placeholder function that the application uses to create or return a singleton instance of Neo4jGraph.
In src/modules/graph.ts, find the initGraph() function.
Unresolved directive in lesson.adoc - include::https://raw.githubusercontent.com/neo4j-graphacademy/llm-chatbot-python/main/src/modules/graph.ts[tag=graph]The code (1) defines a variable for storing the Neo4jGraph and (2) implements a function to either return an existing Neo4jGraph object or create a new one if it doesn’t exist, employing the singleton pattern.
Inside the if statement, call the Neo4jGraph.initialize() method, passing the url, username, and password defined in the environment variables.
Unresolved directive in lesson.adoc - include::https://raw.githubusercontent.com/neo4j-graphacademy/llm-chatbot-python/main/src/solutions/modules/graph.ts[tag=create, indent=0]The Neo4jGraph.initialize() method will create a new Neo4jGraph instance and verify connectivity to the database.
Verifying connectivity ensures that the Neo4j credentials are correct and throws an error if the application cannot establish a connection.
Unresolved directive in lesson.adoc - include::https://raw.githubusercontent.com/neo4j-graphacademy/llm-chatbot-python/main/src/solutions/modules/graph.ts[tag=return, indent=0]If you have followed the instructions correctly, your initGraph function should resemble the following:
Unresolved directive in lesson.adoc - include::https://raw.githubusercontent.com/neo4j-graphacademy/llm-chatbot-python/main/src/solutions/modules/graph.ts[tag=graph, indent=0]Testing your changes
If you have followed the instructions, you should be able to run the following unit test to verify the response using the npm run test command.
npm run test graph.test.tsView Unit Test
Unresolved directive in ../../../../includes/test.adoc - include::https://raw.githubusercontent.com/neo4j-graphacademy/llm-chatbot-python/main/src/modules/graph.test.ts[]Verifying the Test
If every test in the test suite has succeeded, a (:DriverTest) node will be created in your database.
Click the Check Database button below to verify the tests have succeeded.
Hint
You can compare your code with the solution in src/solutions/modules/graph.ts and double-check that the conditions have been met in the test suite.
Solution
You can compare your code with the solution in src/solutions/modules/graph.ts and double-check that the conditions have been met in the test suite.
You can also run the following Cypher statement to double-check that the index has been created in your database.
MATCH (t:DriverTest {working: true})
RETURN count(*)Once you have verified your code and re-ran the tests, click Try again…* to complete the challenge.
Summary
In this lesson, you created a singleton Neo4jGraph object that you will use across the application.
In the next lesson, you will use this object to save and retrieve conversation history.