input: Write a python function to extract text data from a specific class of HTML elements using BeautifulSoup and requests library.
  assert extract_data('http://www.example.com', 'div', 'data-cell') == ['Example Data 1', 'Example Data 2']
  assert extract_data('http://www.example2.com', 'span', 'info') == ['Info 1', 'Info 2', 'Info 3']
  assert extract_data('http://www.example3.com', 'p', 'description') == ['Description 1', 'Description 2']
output: def extract_data(url, tag, class_name):
      import requests
      from bs4 import BeautifulSoup
  
      response = requests.get(url)
      soup = BeautifulSoup(response.content, 'html.parser')
      elements = soup.find_all(tag, class_=class_name)
      
      return [element.get_text(strip=True) for element in elements]