How to use the icrawler.utils.ThreadPool function in icrawler

# -*- coding: utf-8 -*-

import logging
import time
from threading import current_thread

from six.moves import queue
from six.moves.urllib.parse import urlsplit

from icrawler.utils import ThreadPool


class Parser(ThreadPool):
    """Base class for parses.

    Essentially a thread manager, in charge of downloading pages, parsing pages,
    extracting image urls and put them into task_queue.

    Attributes:
        url_queue: A queue storing page urls, connecting Feeder and Parser.
        task_queue: A queue storing image downloading tasks, connecting
                    Parser and Downloader.
        global_signal: A Signal object for cross-module communication.
        session: A requests.Session object.
        logger: A logging.Logger object used for logging.
        threads: A list storing all the threading.Thread objects of the parser.
        thread_num: An integer indicating the number of threads.
        lock: A threading.Lock object.
    """

# -*- coding: utf-8 -*-

import os.path as osp
from threading import current_thread

from icrawler.utils import ThreadPool


class Feeder(ThreadPool):
    """Base class for feeder.

    A thread pool of feeder threads, in charge of feeding urls to parsers.

    Attributes:
        thread_num (int): An integer indicating the number of threads.
        global_signal (Signal): A :class:`Signal` object for communication
            among all threads.
        out_queue (Queue): A queue connected with parsers' inputs,
            storing page urls.
        session (Session): A session object.
        logger (Logger): A logging.Logger object used for logging.
        workers (list): A list storing all the threading.Thread objects
            of the feeder.
        lock (Lock): A :class:`Lock` instance shared by all feeder threads.
    """

# -*- coding: utf-8 -*-

from threading import current_thread

from PIL import Image
from six import BytesIO
from six.moves import queue
from six.moves.urllib.parse import urlparse

from icrawler.utils import ThreadPool


class Downloader(ThreadPool):
    """Base class for downloader.

    A thread pool of downloader threads, in charge of downloading files and
    saving them in the corresponding paths.

    Attributes:
        task_queue (CachedQueue): A queue storing image downloading tasks,
            connecting :class:`Parser` and :class:`Downloader`.
        signal (Signal): A Signal object shared by all components.
        session (Session): A session object.
        logger: A logging.Logger object used for logging.
        workers (list): A list of downloader threads.
        thread_num (int): The number of downloader threads.
        lock (Lock): A threading.Lock object.
        storage (BaseStorage): storage backend.
    """