Delete thread method for In memory checkpointer.

[Shaveen12]

delete_thread Method for InMemorySaver

The current InMemorySaver class does not have a delete_thread(thread_id) method, which deletes all data related to a particular thread_id and allows the same thread_id to be reused without restarting the server.

I have implemented this method as follows:

class CustomInMemorySaver(InMemorySaver):
    """
    Custom InMemorySaver that allows deleting all data associated with a thread_id.
    """

    def delete_thread(self, thread_id: str) -> None:
        """
        Deletes all checkpoints, writes, and blobs associated with the given thread_id.

        Args:
            thread_id (str): The ID of the thread to delete.
        """
        # Delete from storage
        if thread_id in self.storage:
            del self.storage[thread_id]
            logger.info(f"Deleted checkpoints for thread_id: {thread_id}")

        # Delete from writes
        writes_keys_to_delete = [
            key for key in self.writes if key[0] == thread_id
        ]
        for key in writes_keys_to_delete:
            del self.writes[key]
        if writes_keys_to_delete:
            logger.info(f"Deleted writes for thread_id: {thread_id}")

        # Delete from blobs
        blobs_keys_to_delete = [key for key in self.blobs if key[0] == thread_id]
        for key in blobs_keys_to_delete:
            del self.blobs[key]
        if blobs_keys_to_delete:
            logger.info(f"Deleted blobs for thread_id: {thread_id}")

I would like to contribute this to the main repo.