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