Repository: microsoft/semantic-kernel
File: dotnet/src/SemanticKernel.Core/Functions/ContextualSelection/FunctionStore.cs (C#)

Code before:
    /// <param name="collectionName">The name of the collection to use for storing and retrieving functions.</param>
    /// <param name="vectorDimensions">The number of dimensions to use for the memory embeddings.</param>
    /// <param name="functions">The functions to vectorize and store for searching related functions.</param>
    /// <param name="maxNumberOfFunctions">The maximum number of relevant functions to retrieve from the vector store.</param>
    /// <param name="loggerFactory">The logger factory to use for logging. If not provided, no logging will be performed.</param>
    /// <param name="options">The options to use for the function store.</param>
    public FunctionStore(
        VectorStore vectorStore,
        string collectionName,
        int vectorDimensions,
        IEnumerable<AIFunction> functions,
        int maxNumberOfFunctions,
        ILoggerFactory? loggerFactory = default,
        FunctionStoreOptions? options = null)
    {
        Verify.NotNull(vectorStore);
        Verify.NotNullOrWhiteSpace(collectionName);
        Verify.True(vectorDimensions > 0, "Vector dimensions must be greater than 0");
        Verify.NotNull(functions);
        Verify.True(maxNumberOfFunctions > 0, "Max number of functions must be greater than 0");

        this._vectorStore = vectorStore;
        this._collectionName = collectionName;
        this._functionByName = functions.ToDictionary(function => function.Name);
        this._maxNumberOfFunctions = maxNumberOfFunctions;
        this._logger = loggerFactory?.CreateLogger<FunctionStore>() ?? NullLogger.Instance as ILogger;
        this._options = options ?? new FunctionStoreOptions();

        // Create and assert the collection support record keys of string type
        this._collection = this._vectorStore.GetDynamicCollection(collectionName, new VectorStoreCollectionDefinition()
        {
            Properties = [
                new VectorStoreKeyProperty("Name", typeof(string)),
                new VectorStoreVectorProperty("Embedding", typeof(string), dimensions: vectorDimensions)
            ]
        });
    }

    /// <summary>
    /// Saves the functions to the vector store.
    /// </summary>
    /// <param name="cancellationToken">The cancellation token to use for cancellation.</param>
    public async Task SaveAsync(CancellationToken cancellationToken = default)
    {
        // Get function data to vectorize
        var nameSourcePairs = await this.GetFunctionsVectorizationInfoAsync(cancellationToken).ConfigureAwait(false);

        var functionRecords = new List<Dictionary<string, object?>>(nameSourcePairs.Count);

        // Create vector store records
        for (var i = 0; i < nameSourcePairs.Count; i++)

Review comment (suggestion):
nit. Thought `NullLogger.Instance` was already an `ILogger` curious why the cast is needed.

```suggestion
        this._logger = (loggerFactory ?? NullLoggerFactory.Instance).CreateLogger<FunctionStore>();
```

Code after:
    /// <param name="collectionName">The name of the collection to use for storing and retrieving functions.</param>
    /// <param name="vectorDimensions">The number of dimensions to use for the memory embeddings.</param>
    /// <param name="functions">The functions to vectorize and store for searching related functions.</param>
    /// <param name="maxNumberOfFunctions">The maximum number of relevant functions to retrieve from the vector store.</param>
    /// <param name="loggerFactory">The logger factory to use for logging. If not provided, no logging will be performed.</param>
    /// <param name="options">The options to use for the function store.</param>
    internal FunctionStore(
        VectorStore vectorStore,
        string collectionName,
        int vectorDimensions,
        IEnumerable<AIFunction> functions,
        int maxNumberOfFunctions,
        ILoggerFactory? loggerFactory = default,
        FunctionStoreOptions? options = null)
    {
        Verify.NotNull(vectorStore);
        Verify.NotNullOrWhiteSpace(collectionName);
        Verify.True(vectorDimensions > 0, "Vector dimensions must be greater than 0");
        Verify.NotNull(functions);
        Verify.True(maxNumberOfFunctions > 0, "Max number of functions must be greater than 0");

        this._vectorStore = vectorStore;
        this._collectionName = collectionName;
        this._functionByName = functions.ToDictionary(function => function.Name);
        this._maxNumberOfFunctions = maxNumberOfFunctions;
        this._logger = (loggerFactory ?? NullLoggerFactory.Instance).CreateLogger<FunctionStore>();
        this._options = options ?? new FunctionStoreOptions();

        // Create and assert the collection support record keys of string type
        this._collection = this._vectorStore.GetDynamicCollection(collectionName, new VectorStoreCollectionDefinition()
        {
            Properties = [
                new VectorStoreKeyProperty("Name", typeof(string)),
                new VectorStoreVectorProperty("Embedding", typeof(string), dimensions: vectorDimensions)
            ]
        });
    }

    /// <summary>
    /// Saves the functions to the vector store.
    /// </summary>
    /// <param name="cancellationToken">The cancellation token to use for cancellation.</param>
    public async Task SaveAsync(CancellationToken cancellationToken = default)
    {
        // Get function data to vectorize
        var nameSourcePairs = await this.GetFunctionsVectorizationInfoAsync(cancellationToken).ConfigureAwait(false);

        var functionRecords = new List<Dictionary<string, object?>>(nameSourcePairs.Count);

        // Create vector store records
        for (var i = 0; i < nameSourcePairs.Count; i++)