How does `timestamp_format` parameter work when loading to BigQuery using LoadJobConfig

I'm having some issues getting data into BigQuery which is currently stored as CSVs in GCS.

Checking the data, fields I'm uploading as timestamps have 2 different format:

2025-12-04 08:17:35.970000000 2025-12-04 09:37:00

In this case, removing timestamp_format it will work fine. But I know for some CSVs, they have a different format, so I'd like to get it working with this parameter.

However, I'm unsure the syntax for writing the format I need to use, and also if there's a way to include optional milliseconds.

job_config = bigquery.LoadJobConfig( schema=target_table_schema, skip_leading_rows=1, field_delimiter="|", source_format=bigquery.SourceFormat.CSV, write_disposition='WRITE_TRUNCATE', encoding='UTF-16LE', timestamp_format="yyyy-MM-dd HH:mm:ss.SSS", )