import mutations

class UserSignup(mutations.Mutation):
    """Define the inputs to your mutation here. """
    email = mutations.fields.CharField(required=True)
    full_name = mutations.fields.CharField(required=True)
    send_welcome_email = mutations.fields.Boolean(required=False, default=True)

    def validate_email_address(self):
        """Custom validation for a field.

        If you encounter any validation errors and want to raise, you should
        raise mutation.ValidationError or some sublcass thereof. Otherwise, it
        assumes there were no problems.

        Any function beginning with `validate_` is assumed to be a validator
        function and will be run before the mutation can execute.
        """
        if not self.email.is_valid():
            raise mutations.ValidationError("email_not_valid", "Email is not valid.")

    def execute(self):
        """Executes the mutation.

        This method does the heavy lifting. You can call it by calling .run() on
        your mutation class.
        """
        user = User.objects.create(email=self.email, name=self.full_name)
        if self.send_welcome_email:
            EmailServer.deliver(recipient = self.email)
        return user

>>> result = UserSignup.run(email=email, full_name="Bob Boblob")
>>> result.success
True
>>> result.return_value
<User id=...>
>>> result.errors

result = ...

>>> result = UserSignup.run(email=None)
>>> result.success
False
>>> result.errors
mutations.ErrorDict({
  'email': ['email_not_valid']
})
>>> result.value
None

>>> result = UserSignup.validate(email=email, full_name="Bob Boblob")
>>> result.is_valid
True