def METHOD_NAME(data_entry,
                        src_field,
                        dst_field,
                        tokenizer):
    """
    Create a re-tokenized field from an existing one.
    :param data_entry:   a dictionary of entries (keys are field names, values are text items)
    :param src_field:    a source field
    :param dst_field:    a target field
    :param tokenizer:    a tokenizer to use, if None, nothing is done
    """
    if tokenizer is not None:
        dst = ''
        if src_field in data_entry:
            dst = get_retokenized(tokenizer, data_entry[src_field])
        data_entry[dst_field] = ds