input: Write a python function to validate an email address using regex.
  assert validate_email('example@domain.com') == True
  assert validate_email('invalid-email') == False
  assert validate_email('user@domain.co.in') == True
  assert validate_email('user.name@domain.com') == True
  assert validate_email('user@domain@domain.com') == False
output: import re
  
  def validate_email(email):
      pattern = r'^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$'
      return re.match(pattern, email) is not None