code: def _record_field_to_json(fields, row_value):
      
      record = {}
      isdict = isinstance(row_value, dict)
  
      for subindex, subfield in enumerate(fields):
          subname = subfield.name
          if isdict:
              subvalue = row_value.get(subname)
          else:
              subvalue = row_value[subindex]
          record[subname] = _field_to_json(subfield, subvalue)
      return record
docs: Convert a record/struct field to its JSON representation.
  
      Args:
          fields ( \
              Sequence[:class:`~google.cloud.bigquery.schema.SchemaField`], \
          ):
              The :class:`~google.cloud.bigquery.schema.SchemaField`s of the
              record's subfields to use for type conversion and field names.
          row_value (Union[Tuple[Any], Mapping[str, Any]):
              A tuple or dictionary to convert to JSON-serializable values.
  
      Returns:
          Mapping[str, any]:
              A JSON-serializable dictionary.