How to use the beets.library.Item function in beets

def test_flex_field_type(self):
        class RatingPlugin(plugins.BeetsPlugin):
            item_types = {'rating': types.Float()}

        self.register_plugin(RatingPlugin)
        self.config['plugins'] = 'rating'

        item = Item(path=u'apath', artist=u'aaa')
        item.add(self.lib)

        # Do not match unset values
        out = self.run_with_output(u'ls', u'rating:1..3')
        self.assertNotIn(u'aaa', out)

        self.run_command(u'modify', u'rating=2', u'--yes')

        # Match in range
        out = self.run_with_output(u'ls', u'rating:1..3')
        self.assertIn(u'aaa', out)

        # Don't match out of range
        out = self.run_with_output(u'ls', u'rating:3..5')
        self.assertNotIn(u'aaa', out)

def test_matches(self):
        spl = SmartPlaylistPlugin()

        a = MagicMock(Album)
        i = MagicMock(Item)

        self.assertFalse(spl.matches(i, None, None))
        self.assertFalse(spl.matches(a, None, None))

        query = Mock()
        query.match.side_effect = {i: True}.__getitem__
        self.assertTrue(spl.matches(i, query, None))
        self.assertFalse(spl.matches(a, query, None))

        a_query = Mock()
        a_query.match.side_effect = {a: True}.__getitem__
        self.assertFalse(spl.matches(i, None, a_query))
        self.assertTrue(spl.matches(a, None, a_query))

        self.assertTrue(spl.matches(i, query, a_query))
        self.assertTrue(spl.matches(a, query, a_query))

def boracay(l): return beets.library.Item(l.conn.execute('select * from items '
    'where id=3').fetchone())

def add_album_fixture(self, track_count=1, ext='mp3'):
        """Add an album with files to the database.
        """
        items = []
        path = os.path.join(_common.RSRC, 'full.' + ext)
        for i in range(track_count):
            item = Item.from_path(str(path))
            item.album = u'\u00e4lbum'  # Check unicode paths
            item.title = u't\u00eftle {0}'.format(i)
            item.add(self.lib)
            item.move(copy=True)
            item.store()
            items.append(item)
        return self.lib.add_album(items)

# requires parsing the configuration.
    if ctx.invoked_subcommand == 'config':
        return

    # Configure the MusicBrainz API.
    mb.configure()

    # Open the library database and set it on the context
    # if we didn't already get it from the test suite.
    if not beets_ctx.lib:
        beets_ctx.lib = _open_library(config)

    plugins.send('library_opened', lib=beets_ctx.lib)

    # Load field types from the plugins.
    library.Item._types.update(plugins.types(library.Item))
    library.Album._types.update(plugins.types(library.Album))

    # Tell plugins when the subcommand invocation is finished.
    @ctx.call_on_close
    def send_plugin_cli_exit():
        plugins.send('cli_exit', lib=beets_ctx.lib)

def track_to_item(track):
    data = {}
    for dname, bname in FIELD_MAP.items():
        data[bname] = track[dname]
    data['length'] = float(track['tracklen']) / 1000
    data['path'] = track.ipod_filename()
    return Item(data)

def _get_fields(only_writable):
    # I have seen it suggested that this is currently the thing to do.
    # Notably you cannot use library.MediaFile.fields(), which returns
    # fields that don't exist on Items such as "date", or so I've
    # decided based on experimental evidence.
    return [field for field in library.Item._fields.keys()
            if not only_writable or field not in READ_ONLY_FIELDS]

# Start generating the script
    yield u"_beet() {\n"

    # Command names
    yield u"  local commands='%s'\n" % ' '.join(command_names)
    yield u"\n"

    # Command aliases
    yield u"  local aliases='%s'\n" % ' '.join(aliases.keys())
    for alias, cmd in aliases.items():
        yield u"  local alias__%s=%s\n" % (alias, cmd)
    yield u'\n'

    # Fields
    yield u"  fields='%s'\n" % ' '.join(
        set(library.Item._fields.keys() + library.Album._fields.keys())
    )

    # Command options
    for cmd, opts in options.items():
        for option_type, option_list in opts.items():
            if option_list:
                option_list = ' '.join(option_list)
                yield u"  local %s__%s='%s'\n" % (
                    option_type, cmd, option_list)

    yield u'  _beet_dispatch\n'
    yield u'}\n'

def _merge(self, objs):
        """Merge duplicate items. See ``_merge_items`` and ``_merge_albums``
        for the relevant strategies.
        """
        kind = Item if all(isinstance(o, Item) for o in objs) else Album
        if kind is Item:
            objs = self._merge_items(objs)
        else:
            objs = self._merge_albums(objs)
        return objs