Python: Parallel function calling sample (#8682)

### Motivation and Context

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Customers are having questions about parallel function calling and
whether the kernel will execute functions in parallel.
### Description
<!-- Describe your changes, the overall approach, the underlying design.
These notes will help understanding how your code works. Thanks! -->
Add a sample to show that the kernel will execute functions in parallel
when the model returns parallel function calls.

### Contribution Checklist

<!-- Before submitting this PR, please make sure: -->

- [x] The code builds clean without any errors or warnings
- [x] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [x] All unit tests pass, and I have added new tests where possible
- [x] I didn't break anyone 😄

---------

Co-authored-by: Evan Mattson <35585003+moonbox3@users.noreply.github.com>

python/samples/concepts/auto_function_calling/parallel_function_calling.py

@@ -0,0 +1,102 @@
+# Copyright (c) Microsoft. All rights reserved.
+
+import asyncio
+import logging
+import sys
+import time
+from typing import Annotated
+
+from semantic_kernel.connectors.ai.function_choice_behavior import FunctionChoiceBehavior
+from semantic_kernel.connectors.ai.open_ai.services.open_ai_chat_completion import OpenAIChatCompletion
+from semantic_kernel.connectors.ai.prompt_execution_settings import PromptExecutionSettings
+from semantic_kernel.functions.kernel_arguments import KernelArguments
+from semantic_kernel.functions.kernel_function_decorator import kernel_function
+from semantic_kernel.kernel import Kernel
+
+# This sample demonstrates how the kernel will execute functions in parallel.
+# The output of this sample should look similar to the following:
+#
+# [2024-09-11 10:15:35.070 INFO] processing 2 tool calls in parallel.
+# The employee with ID 123 is named John Doe and they are 30 years old.
+# Time elapsed: 11.96s
+#
+# The mock plugin simulates a long-running operation to fetch the employee's name and age.
+# When you run the sample, you should see the total execution time is less than the sum
+# of the two function calls because the kernel executes the functions in parallel.
+
+# This concept example shows how to handle both streaming and non-streaming responses
+# To toggle the behavior, set the following flag accordingly:
+stream = True
+
+
+def set_up_logging():
+    """Set up logging to verify the kernel execute the functions in parallel"""
+    root_logger = logging.getLogger()
+    root_logger.setLevel(logging.INFO)
+
+    handler = logging.StreamHandler(sys.stdout)
+    handler.setLevel(logging.INFO)
+    handler.setFormatter(
+        logging.Formatter("[%(asctime)s.%(msecs)03d %(levelname)s] %(message)s", datefmt="%Y-%m-%d %H:%M:%S"),
+    )
+    # Print only the logs from the chat completion client to reduce the output of the sample
+    handler.addFilter(lambda record: record.name == "semantic_kernel.connectors.ai.chat_completion_client_base")
+
+    root_logger.addHandler(handler)
+
+
+class EmployeePlugin:
+    """A mock plugin to simulate a plugin that fetches employee information"""
+
+    @kernel_function(name="get_name", description="Find the name of the employee by the id")
+    async def get_name(
+        self, id: Annotated[str, "The ID of the employee"]
+    ) -> Annotated[str, "The name of the employee"]:
+        # Simulate a long-running operation
+        await asyncio.sleep(10)
+        return "John Doe"
+
+    @kernel_function(name="get_age", description="Get the age of the employee by the id")
+    async def get_age(self, id: Annotated[str, "The ID of the employee"]) -> Annotated[int, "The age of the employee"]:
+        # Simulate a long-running operation
+        await asyncio.sleep(10)
+        return 30
+
+
+async def main():
+    kernel = Kernel()
+    kernel.add_service(OpenAIChatCompletion(service_id="open_ai"))
+    kernel.add_plugin(EmployeePlugin(), "EmployeePlugin")
+
+    # With this query, the model will call the get_name and get_age functions in parallel.
+    # Note that for certain queries, the model may choose to call the functions sequentially.
+    # For example, if the available functions are `get_email_by_id` and `get_name_by_email`,
+    # the model will not be able to call them in parallel because the second function depends
+    # on the result of the first function.
+    query = "What is the name and age of the employee of ID 123?"
+    arguments = KernelArguments(
+        settings=PromptExecutionSettings(
+            # Set the function_choice_behavior to auto to let the model
+            # decide which function to use, and let the kernel automatically
+            # execute the functions.
+            function_choice_behavior=FunctionChoiceBehavior.Auto(),
+        )
+    )
+
+    start = time.perf_counter()
+
+    if stream:
+        async for result in kernel.invoke_prompt_stream(query, arguments=arguments):
+            print(str(result[0]), end="")
+        print()
+    else:
+        result = await kernel.invoke_prompt(query, arguments=arguments)
+        print(result)
+
+    print(f"Time elapsed: {time.perf_counter() - start:.2f}s")
+
+
+if __name__ == "__main__":
+    set_up_logging()
+
+    asyncio.run(main())