input: Write a function to extract all public email addresses from a given string using a regular expression. Return a list of all email addresses found within the input text. If there are no email addresses, return an empty list. The function should be able to handle various email formats.
  assert extract_emails("My email is john@example.com and yours is john@gmail.com") == ["john@example.com", "john@gmail.com"]
  assert extract_emails("There are no emails here") == []
  assert extract_emails("Contact us at support@company.org or info@helpdesk.biz") == ["support@company.org", "info@helpdesk.biz"]
  assert extract_emails("") == []
output: import re
  
  def extract_emails(text):
      pattern = r'[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}'
      return re.findall(pattern, text)