input: Write a function to extract all email addresses from a given string using regular expressions. Return a list of all found email addresses. If the string is empty, 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("invalid@email, but valid@example.com")==['valid@example.com']
  assert find_emails("")==[]
output: import re
  
  def find_emails(text):
      pattern = r'[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+'
      return re.findall(pattern, text)