input: Write a function that extracts all email addresses from a given string. If the given string is empty then return an empty list. Use a regular expression to match the email addresses.
  assert find_emails("This is an example with two emails: john@example.com, and jane@example.com")==['john@example.com', 'jane@example.com']
  assert find_emails("No emails in this string.")==[]
  assert find_emails("")==[]
output: import re
  
  def find_emails(text):
      return re.findall(r'[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}', text)