Allow JSON type in TableSchema for WriteToBigQuery with FILE_LOAD method in Python SDK

[sapphire008]

Removing the JSON type check when using WriteToBigQuery with FILE_LOAD method in Python SDK. Throwing a warning instead.

• Related to the change in Java SDK: Allow JSON type in TableSchema for BigQuery FILE_LOAD #29923. Consistent with this PR for Java SDK, I have changed the raise ValueError to a logging.warn`.
• Relevant lines of code
  

  beam/sdks/python/apache_beam/io/gcp/bigquery.py

  Lines 2178 to 2191 in 8a74a1c

  	def find_in_nested_dict(schema):
  	for field in schema['fields']:
  	if field['type'] == 'JSON':
  	raise ValueError(
  	'Found JSON type in table schema. JSON data '
  	'insertion is currently not supported with '
  	'FILE_LOADS write method. This is supported with '
  	'STREAMING_INSERTS. For more information: '
  	'https://cloud.google.com/bigquery/docs/reference/'
  	'standard-sql/json-data#ingest_json_data')
  	elif field['type'] == 'STRUCT':
  	find_in_nested_dict(field)
  	find_in_nested_dict(self.schema)

I did some hackish testing against a table of my own and it was able to insert the json fields correctly without a problem.

NOT RECOMMENDED but it solves the problem for those who need this tomorrow:

In my docker file that has Apache Beam installed, I used sed to replace the check:

RUN sed -i 's/if field\['\''type'\''\] == '\''JSON'\'':/if field\['\''type'\''\] == '\''JSON_IS_OKAY'\'':/g' /usr/local/lib/python3.11/site-packages/apache_beam/io/gcp/bigquery.py

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