How to use the pybliometrics.scopus.utils.listify function in pybliometrics

Notes
        -----
        The files are cached in ~/.scopus/author_retrieval/ENHANCED/{author_id}
        (without eventually leading '9-s2.0-').
        """
        # Load json
        view = "ENHANCED"  # In case Scopus adds different views in future
        self._id = str(int(str(author_id).split('-')[-1]))
        Retrieval.__init__(self, identifier=self._id, api='AuthorRetrieval',
                           refresh=refresh, view=view)
        self._json = self._json['author-retrieval-response']
        # Checks
        try:
            self._json = self._json[0]
        except KeyError:  # Incomplete forward
            alias_json = listify(self._json['alias']['prism:url'])
            alias = ', '.join([d['$'].split(':')[-1] for d in alias_json])
            text = 'Author profile with ID {} has been merged and the main '\
                   'profile is now one of {}.  Please update your records '\
                   'manually.  Functionality of this object is '\
                   'reduced.'.format(author_id, alias)
            warn(text, UserWarning)

def journal_history(self):
        """List of named tuples of authored publications in the form
        (sourcetitle, abbreviation, type, issn).  issn is only given
        for journals.  abbreviation and issn may be None.
        """
        jour = namedtuple('Journal', 'sourcetitle abbreviation type issn')
        path = ['author-profile', 'journal-history', 'journal']
        hist = [jour(sourcetitle=pub.get('sourcetitle'), issn=pub.get('issn'),
                     abbreviation=pub.get('sourcetitle-abbrev'),
                     type=pub.get('@type'))
                for pub in listify(chained_get(self._json, path, []))]
        return hist or None

def chemicals(self):
        """List of namedtuples representing chemical entities in the form
        (source, chemical_name, cas_registry_number).  In case multiple
        numbers given, they are joined on ";".
        """
        path = ['enhancement', 'chemicalgroup', 'chemicals']
        items = listify(chained_get(self._head, path, []))
        fields = 'source chemical_name cas_registry_number'
        chemical = namedtuple('Chemical', fields)
        out = []
        for item in items:
            for chem in listify(item['chemical']):
                number = chem.get('cas-registry-number')
                try:  # Multiple numbers given
                    num = ";".join([n['$'] for n in number])
                except TypeError:
                    num = number
                new = chemical(source=item['@source'], cas_registry_number=num,
                               chemical_name=chem['chemical-name'])
                out.append(new)
        return out or None

when it lookes correct in the web view.  In this case please request
        a correction.
        """
        out = []
        fields = 'affiliation_id dptid organization city postalcode '\
                 'addresspart country auid indexed_name surname given_name'
        auth = namedtuple('Author', fields)
        items = listify(self._head.get('author-group', []))
        index_path = ['preferred-name', 'ce:indexed-name']
        for item in items:
            if not item:
                continue
            # Affiliation information
            aff = item.get('affiliation', {})
            try:
                aff_ids = listify(aff['affiliation-id'])
                aff_id = ", ".join([a["@afid"] for a in aff_ids])
            except KeyError:
                aff_id = aff.get("@afid")
            org = _get_org(aff)
            # Author information (might relate to collaborations)
            authors = listify(item.get('author', item.get('collaboration', [])))
            for au in authors:
                try:
                    given = au.get('ce:given-name', au['ce:initials'])
                except KeyError:  # Collaboration
                    given = au.get('ce:text')
                new = auth(affiliation_id=aff_id, organization=org,
                           city=aff.get('city'), dptid=aff.get("@dptid"),
                           postalcode=aff.get('postal-code'),
                           addresspart=aff.get('address-part'),
                           country=aff.get('country'), auid=au.get('@auid'),

if self._view == "REF":
            path = ['references', 'reference']
        else:
            path = ['item', 'bibrecord', 'tail', 'bibliography', 'reference']
        items = listify(chained_get(self._json, path, []))
        for item in items:
            info = item.get('ref-info', item)
            volisspag = info.get('volisspag', {}) or {}
            if isinstance(volisspag, list):
                volisspag = volisspag[0]
            volis = volisspag.get("voliss", {})
            if isinstance(volis, list):
                volis = volis[0]
            # Parse author information
            try:  # FULL view parsing
                auth = listify(item['ref-info']['ref-authors']['author'])
                authors = [', '.join([d['ce:surname'], d['ce:initials']])
                           for d in auth]
                auids = None
                affids = None
            except KeyError:  # REF view parsing
                auth = (info.get('author-list') or {}).get('author', [])
                authors = [', '.join(filter(None, [d.get('ce:surname'),
                                                   d.get('ce:given-name')]))
                           for d in auth]
                auids = "; ".join(filter(None, [d.get('@auid') for d in auth]))
                affs = filter(None, [d.get('affiliation') for d in auth])
                affids = "; ".join([aff.get('@id') for aff in affs])
            # Parse IDs
            try:
                ids = listify(info['refd-itemidlist']['itemid'])
            except KeyError:

def funding(self):
        """List of namedtuples parsed funding information in the form
        (agency string id acronym country).
        """
        path = ['item', 'xocs:meta', 'xocs:funding-list', 'xocs:funding']
        funds = listify(chained_get(self._json, path, []))
        out = []
        fund = namedtuple('Funding', 'agency string id acronym country')
        for item in funds:
            new = fund(agency=item.get('xocs:funding-agency'),
                string=item.get('xocs:funding-agency-matched-string'),
                id=item.get('xocs:funding-agency-id'),
                acronym=item.get('xocs:funding-agency-acronym'),
                country=item.get('xocs:funding-agency-country'))
            out.append(new)
        return out or None

def name_variants(self):
        """List of named tuples containing variants of the author name with
        number of documents published with that variant.
        """
        fields = 'indexed_name initials surname given_name doc_count'
        variant = namedtuple('Variant', fields)
        path = ['author-profile', 'name-variant']
        out = [variant(indexed_name=var['indexed-name'], surname=var['surname'],
                       doc_count=var.get('@doc-count'), initials=var['initials'],
                       given_name=var.get('given-name'))
               for var in listify(chained_get(self._json, path, []))]
        return out or None

auth = namedtuple('Author', fields)
        items = listify(self._head.get('author-group', []))
        index_path = ['preferred-name', 'ce:indexed-name']
        for item in items:
            if not item:
                continue
            # Affiliation information
            aff = item.get('affiliation', {})
            try:
                aff_ids = listify(aff['affiliation-id'])
                aff_id = ", ".join([a["@afid"] for a in aff_ids])
            except KeyError:
                aff_id = aff.get("@afid")
            org = _get_org(aff)
            # Author information (might relate to collaborations)
            authors = listify(item.get('author', item.get('collaboration', [])))
            for au in authors:
                try:
                    given = au.get('ce:given-name', au['ce:initials'])
                except KeyError:  # Collaboration
                    given = au.get('ce:text')
                new = auth(affiliation_id=aff_id, organization=org,
                           city=aff.get('city'), dptid=aff.get("@dptid"),
                           postalcode=aff.get('postal-code'),
                           addresspart=aff.get('address-part'),
                           country=aff.get('country'), auid=au.get('@auid'),
                           surname=au.get('ce:surname'), given_name=given,
                           indexed_name=chained_get(au, index_path))
                out.append(new)
        return out or None

Note: Requires either the FULL view or REF view of the article.  Might
        be empty even if refcount is positive.  Specific fields can be empty.
        Author lists (authors, authors_auid, authors_affiliationid) may contain
        duplicates but have been filtered of None's.
        """
        out = []
        fields = 'position id doi title authors authors_auid '\
                 'authors_affiliationid sourcetitle publicationyear volume '\
                 'issue first last citedbycount type text fulltext'
        ref = namedtuple('Reference', fields)
        if self._view == "REF":
            path = ['references', 'reference']
        else:
            path = ['item', 'bibrecord', 'tail', 'bibliography', 'reference']
        items = listify(chained_get(self._json, path, []))
        for item in items:
            info = item.get('ref-info', item)
            volisspag = info.get('volisspag', {}) or {}
            if isinstance(volisspag, list):
                volisspag = volisspag[0]
            volis = volisspag.get("voliss", {})
            if isinstance(volis, list):
                volis = volis[0]
            # Parse author information
            try:  # FULL view parsing
                auth = listify(item['ref-info']['ref-authors']['author'])
                authors = [', '.join([d['ce:surname'], d['ce:initials']])
                           for d in auth]
                auids = None
                affids = None
            except KeyError:  # REF view parsing

def isbn(self):
        """ISBNs belonging to publicationName as tuple of variying length,
        (e.g. ISBN-10 or ISBN-13)."""
        isbns = listify(chained_get(self._head, ['source', 'isbn'], []))
        if len(isbns) == 0:
            return None
        else:
            return tuple((i['$'] for i in isbns))