How to use the pydash.head function in pydash

def test_head(case, expected):
    assert _.head(case) == expected

if not _pairings.where(user_unique_id=user_unique_id, player_id=player_id):
		# Insert pairing
		pairing = DataObject(user_unique_id=user_unique_id, player_id=player_id)
		_pairings.insert(pairing)
		# Insert pair's user to cache
		user = _.head(_users.where(unique_id=user_unique_id))
		if user:
			_cached_users.delete(unique_id=user.unique_id)
			_cached_users.insert(DataObject(unique_id=user.unique_id, name=user.name))
		# Insert pair's player to cache
		result = _battle_players.where(id=player_id)
		if not result:
			result = _prebattle_players.where(id=player_id)
		if not result:
			result = _me_player.where(id=player_id)
		player = _.head(result)
		if player:
			_cached_players.delete(id=player.id)
			_cached_players.insert(DataObject(id=player.id, name=player.name))
		# Notify listeners
		messages.publish(PairingMessage("added", pairing))

players = Table()
		players.create_index('id', unique=True)
		pairings = Table()
		pairings.create_index('player_id')
		pairings.create_index('user_unique_id')

		# Load old 0.6.x cache file
		parser = ConfigParser.ConfigParser()
		with open(source_filepath, "rb") as file:
			parser.readfp(file)

		# Build new cache structures
		users.insert_many(DataObject(unique_id=id, name=name) for name, id in parser.items("TeamSpeakUsers"))
		players.insert_many(DataObject(id=int(id), name=name) for name, id in parser.items("GamePlayers"))
		for user_name, player_names in parser.items("UserPlayerPairings"):
			userid = _.head(users.where(name=user_name)).unique_id
			for player_name in list(csv.reader([player_names]))[0]:
				playerid = _.head(players.where(name=player_name)).id
				pairings.insert(DataObject(player_id=int(playerid), user_unique_id=userid))

		# Remove users & players which do not exist in pairings
		for user in users.clone():
			if not pairings.where(user_unique_id=user.unique_id):
				users.remove(user)
		for player in players.clone():
			if not pairings.where(player_id=player.id):
				players.remove(player)

		# create destination directory if it doesn't exist yet
		if not os.path.isdir(dest_dirpath):
			os.makedirs(dest_dirpath)

def self_desc(cls):
    '''Method to get self description, used at init.'''
    desc_list = [f'{get_class_name(cls)}:']
    for k, v in get_class_attr(cls).items():
        if k == 'spec':
            desc_v = v['name']
        elif ps.is_dict(v) or ps.is_dict(ps.head(v)):
            desc_v = pformat(v)
        else:
            desc_v = v
        desc_list.append(f'- {k} = {desc_v}')
    desc = '\n'.join(desc_list)
    return desc

def remove_user(id):
	old_user = _.head(_users.where(id=id))
	if not old_user:
		return
	_users.remove(old_user)
	messages.publish(UserMessage("removed", old_user))

def get_my_vehicle():
	player = _.head(_me_player)
	if player:
		return _.head(_vehicles.where(player_id=player.id))

def remove_vehicle(id):
	vehicle = _.head(_vehicles.where(id=id))
	if vehicle:
		_vehicles.remove(vehicle)
		messages.publish(VehicleMessage("removed", vehicle))

pairings = Table()
		pairings.create_index('player_id')
		pairings.create_index('user_unique_id')

		# Load old 0.6.x cache file
		parser = ConfigParser.ConfigParser()
		with open(source_filepath, "rb") as file:
			parser.readfp(file)

		# Build new cache structures
		users.insert_many(DataObject(unique_id=id, name=name) for name, id in parser.items("TeamSpeakUsers"))
		players.insert_many(DataObject(id=int(id), name=name) for name, id in parser.items("GamePlayers"))
		for user_name, player_names in parser.items("UserPlayerPairings"):
			userid = _.head(users.where(name=user_name)).unique_id
			for player_name in list(csv.reader([player_names]))[0]:
				playerid = _.head(players.where(name=player_name)).id
				pairings.insert(DataObject(player_id=int(playerid), user_unique_id=userid))

		# Remove users & players which do not exist in pairings
		for user in users.clone():
			if not pairings.where(user_unique_id=user.unique_id):
				users.remove(user)
		for player in players.clone():
			if not pairings.where(player_id=player.id):
				players.remove(player)

		# create destination directory if it doesn't exist yet
		if not os.path.isdir(dest_dirpath):
			os.makedirs(dest_dirpath)

		# write out the new cache files
		users.json_export(users_filepath)