input: Write a python function to send emails to a list of users.
  assert emailUsers([{'email': 'test1@example.com'}, {'email': 'test2@example.com'}])==None
  assert emailUsers([{'email': 'user1@example.com'}, {'email': 'user2@example.com'}, {'email': 'user3@example.com'}])==None
output: def emailUsers(users):
      import smtplib
      from email.mime.text import MIMEText
      from email.mime.multipart import MIMEMultipart
      
      sender_email = "your_email@example.com"
      sender_password = "your_password"
      
      smtp_server = "smtp.example.com"
      smtp_port = 587
      
      subject = "Subject"
      body = "This is a test email."
      
      for user in users:
          receiver_email = user['email']
          
          msg = MIMEMultipart()
          msg['From'] = sender_email
          msg['To'] = receiver_email
          msg['Subject'] = subject
          
          msg.attach(MIMEText(body, 'plain'))
          
          try:
              server = smtplib.SMTP(smtp_server, smtp_port)
              server.starttls()
              server.login(sender_email, sender_password)
              text = msg.as_string()
              server.sendmail(sender_email, receiver_email, text)
              server.quit()
          except Exception as e:
              print(f"Failed to send email to {receiver_email}: {e}")