input: Write a function to extract all email addresses from a given string. The function should use a regular expression to identify and return all valid email addresses found in the input string. If no email addresses are found, the function should return an empty list.
  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 here")==[]
  assert find_emails("")==[]
  assert find_emails("check this out: invalid@email, and valid@email.com")==['valid@email.com']
  assert find_emails("multiple@email.com, and more@email.com, plus extra@domain.net")==['multiple@email.com', 'more@email.com', 'extra@domain.net']
output: import re
  
  def find_emails(text):
      pattern = r'[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}'
      return re.findall(pattern, text)