Originally raised in googleapis/python-spanner-django#566, Spanner will infer the type of a null value if it is not provided but the emulator will throw an error for the same request. This has become an issue for Python ORMs as the suggestion to add this type inference logic to the DBAPI adapter is complicated and requires many changes.

Adding type inference for null values to the emulator to match the production behaviour would resolve the problem and allow us to confidently test against the emulator again.