How to use the pyserini.search.Document function in pyserini

def test_doc_int(self):
        # The doc method is overloaded: if input is int, it's assumed to be a Lucene internal docid.
        doc = self.searcher.doc(1)
        self.assertTrue(isinstance(doc, Document))

        # These are all equivalent ways to get the docid.
        self.assertEqual('CACM-0002', doc.id())
        self.assertEqual('CACM-0002', doc.docid())
        self.assertEqual('CACM-0002', doc.get('id'))
        self.assertEqual('CACM-0002', doc.lucene_document().getField('id').stringValue())

        # These are all equivalent ways to get the 'raw' field
        self.assertEqual(186, len(doc.raw()))
        self.assertEqual(186, len(doc.get('raw')))
        self.assertEqual(186, len(doc.lucene_document().get('raw')))
        self.assertEqual(186, len(doc.lucene_document().getField('raw').stringValue()))

        # These are all equivalent ways to get the 'contents' field
        self.assertEqual(154, len(doc.contents()))
        self.assertEqual(154, len(doc.get('contents')))

def test_doc_str(self):
        # The doc method is overloaded: if input is str, it's assumed to be an external collection docid.
        doc = self.searcher.doc('CACM-0002')
        self.assertTrue(isinstance(doc, Document))

        # These are all equivalent ways to get the docid.
        self.assertEqual(doc.lucene_document().getField('id').stringValue(), 'CACM-0002')
        self.assertEqual(doc.id(), 'CACM-0002')
        self.assertEqual(doc.docid(), 'CACM-0002')
        self.assertEqual(doc.get('id'), 'CACM-0002')

        # These are all equivalent ways to get the 'raw' field
        self.assertEqual(186, len(doc.raw()))
        self.assertEqual(186, len(doc.get('raw')))
        self.assertEqual(186, len(doc.lucene_document().get('raw')))
        self.assertEqual(186, len(doc.lucene_document().getField('raw').stringValue()))

        # These are all equivalent ways to get the 'contents' field
        self.assertEqual(154, len(doc.contents()))
        self.assertEqual(154, len(doc.get('contents')))

in the index.

        Parameters
        ----------
        docid : str
            The collection ``docid``.

        Returns
        -------
        Optional[Document]
            :class:`Document` corresponding to the ``docid``.
        """
        lucene_document = self.object.document(self.reader, JString(docid))
        if lucene_document is None:
            return None
        return Document(lucene_document)

Parameters
        ----------
        field : str
            The field to look up.
        q : str
            The document's unique id.

        Returns
        -------
        Optional[Document]
            :class:`Document` whose ``field`` is ``id``.
        """
        lucene_document = self.object.documentByField(self.reader, JString(field), JString(q))
        if lucene_document is None:
            return None
        return Document(lucene_document)