input: Write a python function to extract all email addresses from a given text.
  assert extract_emails("Please contact us at support@example.com for more info.") == ["support@example.com"]
  assert extract_emails("Send your feedback to feedback@example.com, sales@example.com.") == ["feedback@example.com", "sales@example.com"]
  assert extract_emails("No emails here!") == []
  assert extract_emails("Emails: first.email@example.com, second.email@domain.co.uk") == ["first.email@example.com", "second.email@domain.co.uk"]
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)