* Multi-column support

* Remove 'rows' field in results, as it's not used by the Javascript. Also, add a test for the multi-column case.

* reformat

* Fix test_bigquery.py tests, remove unnecessary mocking of GraphServer

* reformat

…ook code; also, allow visualization when only some columns are json. (#102)

* Multi-column support

* Remove 'rows' field in results, as it's not used by the Javascript. Also, add a test for the multi-column case.

* reformat

* Fix test_bigquery.py tests, remove unnecessary mocking of GraphServer

* reformat

* Get basic graph visualization working against latest spanner code

* Fix unit tests

* Ignore columns we don't know how to visualize for visualization purposes, but still show them in the tabular view, and don't block visualizing remaining columns

* reformat

* Remove unused dependency on networkx

* Implement stub callback for node expansion

* Fix  test_bigquery_graph_missing_spanner_deps.

The mock query result must contain valid json so that the visualizer attempts to get launched, in order for the code path we're trying to test to get reached.

* reformat

* Add unit test for GraphServerHandler::handler_post_node_expansion()

* Add test for invalid node expansion request

* reformat

* Tweaks to improve code coverage

* More tweaks to improve code coverage

* avoid list comprehension due to code coverage tooling

* Fix visualization in colab.

Problem is that, even though the port is not used in colab mode, the javascript still throws an error if it's undefined.

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>