input: Write a python function to insert multiple documents into a MongoDB collection.
  assert insert_documents('my_database', 'my_collection', [{"_id": 3, "title": "Task 3"}, {"_id": 4, "title": "Task 4"}]) == [3, 4]
  assert insert_documents('my_database', 'my_collection', [{"_id": 5, "title": "Task 5"}, {"_id": 6, "title": "Task 6"}]) == [5, 6]
  assert insert_documents('my_database', 'my_collection', [{"_id": 7, "title": "Task 7"}, {"_id": 8, "title": "Task 8"}]) == [7, 8]
output: def insert_documents(db_name, collection_name, documents):
      from pymongo import MongoClient
  
      client = MongoClient()
      db = client[db_name]
      collection = db[collection_name]
      
      result = collection.insert_many(documents)
      return result.inserted_ids