input: Write a function to send automated emails to a list of recipients. The function should iterate over the list of email addresses and send an email to each address. If the email is sent successfully, it should print 'Email sent successfully.'.
  assert send_emails(["email1@example.com","email2@example.com"])==None
  assert send_emails(["email3@example.com"])==None
  assert send_emails([])==None
output: def send_emails(recipients):
      for email in recipients:
          print('Email sent successfully.')