docs: A few minor fixes for the notebook of Graph QA chain (googleapis#120)

* Add Spanner Graph QA Chain

* Formatted notebook. Added copyright message to prompts file.

* Add missing imports for random graph name

* Make input table name randomized in integration tests to avoid name collision for tests running parallely from different python environments

* Provide timeout to graph cleanup

* Make default timeout of 300 secs for ddl application

* Increase timeout of integration test

* Change integration test timeout

* Minor formatting fixes

* Make the ddl operations test fixture scoped for the module

* Addressed review comments

* Addressed a few other review comments.

* Remove unused function

* fix type check errors

* Addressed review comments

* Addressed review comments

* Clear default project id from notebook

* Add import statement for SpanerGraphQAChain to notebook

---------

Co-authored-by: Amarnath Mullick <[email protected]>

Author: amullick-git

docs/graph_qa_chain.ipynb

@@ -150,7 +150,7 @@
    "source": [
     "# @markdown Please fill in the value below with your Google Cloud project ID and then run the cell.\n",
     "\n",
-    "PROJECT_ID = \"google.com:cloud-spanner-demo\"  # @param {type:\"string\"}\n",
+    "PROJECT_ID = \"\"  # @param {type:\"string\"}\n",
     "\n",
     "# Set the project id\n",
     "!gcloud config set project {PROJECT_ID}\n",
@@ -494,6 +494,7 @@
    "cell_type": "code",
    "source": [
     "from google.cloud import spanner\n",
+    "from langchain_google_spanner import SpannerGraphQAChain\n",
     "from langchain_google_vertexai import ChatVertexAI\n",
     "from IPython.core.display import HTML\n",
     "\n",