palindrome_signup.py

import mutations

class UserSignup(mutations.Mutation):
    """Sign up the user if and only if their name is a palindrome. """
    name = mutations.fields.CharField()
    email = mutations.fields.CharField()

    def validate_name_is_palindrome(self):
        """
        Since this method is prefixed with validate_, it's assumed to be
        a validator and will be run before the command is executed.

        Validators should either return None (if the validator passes), or
        raise ValidationError with an error message if there is a problem.
        """
        if not is_palindrome(self.name):
            raise mutations.error.ValidationError(f"{self.name} is not a Palindrome!")

    def execute(self):
        """
        This only gets called if the user's name is a palindrome.
        """
        user = User.objects.create([...])