.Net: The Gemini connector throws exceptions in parallel tool calls

[TaoChenOSU]

Describe the bug
This is related to #6281.

Using the Gemini connector results in exceptions. It still invokes the function multiple times. However, instead of returning a poem at the end, it throws an exception:

Unhandled exception. System.NotSupportedException: Runtime type 'Microsoft.SemanticKernel.Connectors.Google.GeminiChatMessageContent' is not supported by polymorphic type 'Microsoft.SemanticKernel.KernelContent'. Path: $.
 ---> System.NotSupportedException: Runtime type 'Microsoft.SemanticKernel.Connectors.Google.GeminiChatMessageContent' is not supported by polymorphic type 'Microsoft.SemanticKernel.KernelContent'.
   at System.Text.Json.ThrowHelper.ThrowNotSupportedException_RuntimeTypeNotSupported(Type baseType, Type runtimeType)
   at System.Text.Json.Serialization.Metadata.PolymorphicTypeResolver.TryGetDerivedJsonTypeInfo(Type runtimeType, JsonTypeInfo& jsonTypeInfo, Object& typeDiscriminator)
   at System.Text.Json.Serialization.JsonConverter.ResolvePolymorphicConverter(Object value, JsonTypeInfo jsonTypeInfo, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   --- End of inner exception stack trace ---
   at System.Text.Json.ThrowHelper.ThrowNotSupportedException(WriteStack& state, NotSupportedException ex)
   at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.Serialize(Utf8JsonWriter writer, T& rootValue, Object rootValueBoxed)
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.SerializeAsObject(Utf8JsonWriter writer, Object rootValue)
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.Serialize(Utf8JsonWriter writer, T& rootValue, Object rootValueBoxed)
   at System.Text.Json.JsonSerializer.WriteNode[TValue](TValue& value, JsonTypeInfo`1 jsonTypeInfo)
   at System.Text.Json.JsonSerializer.SerializeToNode[TValue](TValue value, JsonSerializerOptions options)
   at Microsoft.SemanticKernel.Connectors.Google.Core.GeminiPart.FunctionResponsePart.FunctionResponseEntity..ctor(Object response)
   at Microsoft.SemanticKernel.Connectors.Google.Core.GeminiRequest.CreateGeminiParts(ChatMessageContent content)
   at Microsoft.SemanticKernel.Connectors.Google.Core.GeminiRequest.CreateGeminiContentFromChatMessage(ChatMessageContent message)
   at Microsoft.SemanticKernel.Connectors.Google.Core.GeminiRequest.AddChatMessage(ChatMessageContent message)
   at Microsoft.SemanticKernel.Connectors.Google.Core.GeminiChatCompletionClient.AddToolResponseMessage(ChatHistory chat, GeminiRequest request, GeminiFunctionToolCall tool, FunctionResult functionResponse, String errorMessage)
   at Microsoft.SemanticKernel.Connectors.Google.Core.GeminiChatCompletionClient.ProcessSingleToolCallAsync(ChatCompletionState state, GeminiFunctionToolCall toolCall, CancellationToken cancellationToken)
   at Microsoft.SemanticKernel.Connectors.Google.Core.GeminiChatCompletionClient.ProcessFunctionsAsync(ChatCompletionState state, CancellationToken cancellationToken)
   at Microsoft.SemanticKernel.Connectors.Google.Core.GeminiChatCompletionClient.GenerateChatMessageAsync(ChatHistory chatHistory, PromptExecutionSettings executionSettings, Kernel kernel, CancellationToken cancellationToken)
   at Microsoft.SemanticKernel.ChatCompletion.ChatCompletionServiceExtensions.GetChatMessageContentAsync(IChatCompletionService chatCompletionService, String prompt, PromptExecutionSettings executionSettings, Kernel kernel, CancellationToken cancellationToken)
   at Microsoft.SemanticKernel.KernelFunctionFromPrompt.InvokeCoreAsync(Kernel kernel, KernelArguments arguments, CancellationToken cancellationToken)
   at Microsoft.SemanticKernel.KernelFunction.<>c__DisplayClass21_0.<<InvokeAsync>b__0>d.MoveNext()
--- End of stack trace from previous location ---
   at Microsoft.SemanticKernel.Kernel.InvokeFilterOrFunctionAsync(NonNullCollection`1 functionFilters, Func`2 functionCallback, FunctionInvocationContext context, Int32 index)
   at Program.FirstFunctionFilter.OnFunctionInvocationAsync(FunctionInvocationContext context, Func`2 next) in C:\Users\taochen\Projects\ScratchPad\Program.cs:line 67
   at Microsoft.SemanticKernel.Kernel.InvokeFilterOrFunctionAsync(NonNullCollection`1 functionFilters, Func`2 functionCallback, FunctionInvocationContext context, Int32 index)
   at Microsoft.SemanticKernel.Kernel.OnFunctionInvocationAsync(KernelFunction function, KernelArguments arguments, FunctionResult functionResult, Func`2 functionCallback)
   at Microsoft.SemanticKernel.KernelFunction.InvokeAsync(Kernel kernel, KernelArguments arguments, CancellationToken cancellationToken)
   at Microsoft.SemanticKernel.Kernel.InvokeAsync[TResult](String pluginName, String functionName, KernelArguments arguments, CancellationToken cancellationToken)
   at Program.Main() in C:\Users\taochen\Projects\ScratchPad\Program.cs:line 29
   at Program.<Main>()

To Reproduce
Steps to reproduce the behavior:

1. Follow the repro in: .Net: Invoking kernel function directly with auto invoke enabled results in multiple nested calls to the function #6281
2. Use the Gemini connector instead of the OpenAI connector.
3. Use a Gemini setting: GeminiPromptExecutionSettings settings = new() { ToolCallBehavior = GeminiToolCallBehavior.AutoInvokeKernelFunctions };

Expected behavior
Return a poem.

There won't be any exception and the code correctly returns a poem with auto invoked disabled. This is because the function will only be invoked once.

Platform

• OS: Windows
• IDE: VS Code
• Language: C#
• Source: main branch of repository

Additional context
Tested with gemini-1.0-pro