def _get_aps_tag_values(namespace, mapping):
    """ Get tag values of keys in `mapping` from `namespace`.

    If `namespace` contain several instances of the same tag, for instance
    in the case of "PAR"-tags in description, join them by new-lines.

    Parameters
    ----------
    namespace : uspto_parsing_tools.aps.NameSpace
        Namespace to parse.
    mapping : dict[str, str]
        Tag-names to attribute name-mapping.

    Returns
    -------
    tag_values: dict[str, str]
        Attribute-name to value mapping.
    """
    tag_values = dict()
    for tag_key, attribute_name in mapping.items():
        tags = namespace.get_tags_by_key(tag_key)
        value = '\n'.join(tag.data for tag in tags)
        tag_values[attribute_name] = value

    return tag_values