code: def column_to_bq_schema(self):
          
          kwargs = {}
          if len(self.fields) > 0:
              fields = [field.column_to_bq_schema() for field in self.fields]
              kwargs = {"fields": fields}
  
          return google.cloud.bigquery.SchemaField(self.name, self.dtype,
                                                   self.mode, **kwargs)
docs: Convert a column to a bigquery schema object.