Explain what this is doing line by line:

'''
A module that encapsulates a web scraper. This module scrapes data from a website.
'''
from html.parser import HTMLParser
import urllib.request
from datetime import datetime, timedelta
import logging
from dateutil.parser import parse

class WeatherScraper(HTMLParser):
    """A parser for extracting temperature values from a website."""

    logger = logging.getLogger("main." + __name__)

    def __init__(self):
        try:
            super().__init__()
            self.is_tbody = False
            self.is_td = False
            self.is_tr = False
            self.last_page = False
            self.counter = 0
            self.daily_temps = {}
            self.weather = {}
            self.row_date = ""
        except Exception as error:
            self.logger.error("scrape:init:%s", error)

    def is_valid_date(self, date_str):
        """Check if a given string is a valid date."""

        try:
            parse(date_str, default=datetime(1900, 1, 1))
            return True
        except ValueError:
            return False

    def is_numeric(self, temp_str):
        """Check if given temperature string can be converted to a float."""

        try:
            float(temp_str)
            return True
        except ValueError:
            return False

    def handle_starttag(self, tag, attrs):
        """Handle the opening tags."""

        try:
            if tag == "tbody":
                self.is_tbody = True
            if tag == "tr" and self.is_tbody:
                self.is_tr = True
            if tag == "td" and self.is_tr:
                self.counter += 1
                self.is_td = True

            # Only parses the valid dates, all other values are excluded.
            if tag == "abbr" and self.is_tr and self.is_valid_date(attrs[0][1]):
                self.row_date = str(datetime.strptime(attrs[0][1], "%B %d, %Y").date())

            # if len(attrs) == 2:
            #    if attrs[1][1] == "previous disabled":
            #        self.last_page = True

        except Exception as error:
            self.logger.error("scrape:starttag:%s", error)

    def handle_endtag(self, tag):
        """Handle the closing tags."""

        try:
            if tag == "td":
                self.is_td = False
            if tag == "tr":
                self.counter = 0
                self.is_tr = False
        except Exception as error:
            self.logger.error("scrape:end:%s", error)

    def handle_data(self, data):
        """Handle the data inside the tags."""

        if data.startswith("Daily Data Report for January 2023"):
            self.last_page = True

        try:
            if self.is_tbody and self.is_td and self.counter <= 3 and data.strip():
                if self.counter == 1 and self.is_numeric(data.strip()):
                    self.daily_temps["Max"] = float(data.strip())
                if self.counter == 2 and self.is_numeric(data.strip()):
                    self.daily_temps["Min"] = float(data.strip())
                if self.counter == 3 and self.is_numeric(data.strip()):
                    self.daily_temps["Mean"] = float(data.strip())
                    self.weather[self.row_date] = self.daily_temps
                    self.daily_temps = {}
        except Exception as error:
            self.logger.error("scrape:data:%s", error)

    def get_data(self, initial_date = None, end_date = None):
            """Fetch the weather data and return it as a dictionary of dictionaries."""

            if initial_date is None:
                current_date = datetime.now().date()
            else:
                current_date = initial_date

            while not self.last_page and (end_date is None or current_date > end_date):

                try:
                    url = f"https://climate.weather.gc.ca/climate_data/daily_data_e.html?StationID=27174&timeframe=2&StartYear=1840&EndYear=2018&Day={current_date.day}&Year={current_date.year}&Month={current_date.month}"

                    with urllib.request.urlopen(url) as response:
                        html = response.read().decode()
                    self.feed(html)

                    # Subtracts one day from the current date and assigns the
                    # resulting date back to the current_date variable.
                    current_date -= timedelta(days=1)
                except Exception as error:
                    self.logger.error("scrape:get_data:%s", error)

            return self.weather

# Test program.
if __name__ == "__main__":
    print_data = WeatherScraper().get_data()
    for k, v in print_data.items():
        print(k, v)