input: Write a python function to extract email addresses from a given text.
  assert extract_emails("My email is john@example.com and yours is john@gmail.com") == ["john@example.com", "john@gmail.com"]
  assert extract_emails("Contact us at support@service.com and info@service.com") == ["support@service.com", "info@service.com"]
  assert extract_emails("No emails here!") == []
output: def extract_emails(text):
      import re
      pattern = r'[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}'
      return re.findall(pattern, text)