input: Write a function to extract all email addresses from a given string. The function should return a list of email addresses. If the input string is empty, 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("Multiple emails: alice@example.com, bob@example.net")==['alice@example.com', 'bob@example.net']
  assert find_emails("")==[]
output: def find_emails(text):
      import re
      if not text:
          return []
      pattern = r'[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}'
      return re.findall(pattern, text)