code: def convert_row(self, row, schema, fallbacks):
          
          for index, field in enumerate(schema.fields):
              value = row[index]
              if index in fallbacks:
                  value = _uncast_value(value, field=field)
              else:
                  value = field.cast_value(value)
              row[index] = value
          return row
docs: Convert row to BigQuery