input: Write a function to create a Celery task in Python that sends an email with specified details. The function should take in four parameters: recipient_name, recipient_email, subject, and message. The function should set up the Celery app and define a task that sends the email using the provided details.
  
  from celery import Celery
  from flask_mail import Message
  
  app = Celery('tasks', backend='redis://localhost')
  
  @app.task
  def send_email(recipient_name, recipient_email, subject, message):
   msg = Message(subject, sender='example@example.com', recipients=[recipient_email])
   msg.body = message
   mail.send(msg)
  assert send_email('John Smith', 'john@example.com', 'Hello World', 'This is a test email.')==None
output: def send_email(recipient_name, recipient_email, subject, message):
      msg = Message(subject, sender='example@example.com', recipients=[recipient_email])
      msg.body = message
      mail.send(msg)