input: Write a python function to extract 'href' attributes from all '<a>' tags with class 'post_title' from multiple pages and return them as a list.
  assert crawler(1) == ['https://www.example.com/post1', 'https://www.example.com/post2']
  assert crawler(2) == ['https://www.example.com/post1', 'https://www.example.com/post2', 'https://www.example.com/post3', 'https://www.example.com/post4']
  assert crawler(3) == ['https://www.example.com/post1', 'https://www.example.com/post2', 'https://www.example.com/post3', 'https://www.example.com/post4', 'https://www.example.com/post5', 'https://www.example.com/post6']
output: import requests
  from bs4 import BeautifulSoup
  
  def crawler(pages):
      href_list = []
      base_url = "https://www.example.com/page"
      
      for page in range(1, pages + 1):
          url = f"{base_url}{page}"
          response = requests.get(url)
          soup = BeautifulSoup(response.content, 'html.parser')
          for a_tag in soup.find_all('a', class_='post_title'):
              href_list.append(a_tag.get('href'))
      
      return href_list