input: Write a python function to extract the text inside the <li> tags from a given HTML string.
  assert extract_list_items('<html><head><title>List of Programming Languages</title><style>h1 { font-family: sans-serif; color: #444444; } ul { padding: 0; margin: 0; list-style-type: none; line-height: 1.5; font-family: sans-serif; font-size: 16px; color: #444444; }</style></head><body><h1>List of Programming Languages</h1><ul><li>Java</li><li>Python</li><li>C++</li><li>JavaScript</li><li>C#</li><li>PHP</li><li>Perl</li><li>Ruby</li><li>Objective-C</li><li>Swift</li></ul></body></html>') == ['Java', 'Python', 'C++', 'JavaScript', 'C#', 'PHP', 'Perl', 'Ruby', 'Objective-C', 'Swift']
  assert extract_list_items('<ul><li>HTML</li><li>CSS</li><li>JavaScript</li></ul>') == ['HTML', 'CSS', 'JavaScript']
  assert extract_list_items('<ul><li>Go</li><li>Rust</li><li>Kotlin</li></ul>') == ['Go', 'Rust', 'Kotlin']
output: def extract_list_items(html):
      from bs4 import BeautifulSoup
      
      soup = BeautifulSoup(html, 'html.parser')
      list_items = soup.find_all('li')
      
      return [item.get_text() for item in list_items]