What is the correct mutation class code for Graphcool createUser Mutation?

Question

I'm getting started with Relay and GraphCool and have trouble creating the createUser Mutation with Relay.

This is my current code:

import Relay from 'react-relay';

class SignupUserMutation extends Relay.Mutation {

getMutation() {
    return Relay.QL`
        mutation {
            createUser(input: {
                authProvider: {email: { email: $email, password: $password }},
                clientMutationId: "createuser1"
            }) {
                clientMutationId
            }
        }
    `;
}

getVariables() {
    return {
        email:    this.props.email,
        password: this.props.password
    };
}

getFatQuery() {
    return Relay.QL`
        fragment on CreateUserPayload {
            viewer { id }
        }
    `;
}

getConfigs() {
    return [{
        type:           'RANGE_ADD',
        parentName:     'viewer',
        parentID:       this.props.viewerId,
        connectionName: 'users',
        edgeName:       'usereEdge',
        rangeBehaviors: {
            '': 'append',
        },
    }];
}

}

export default SignupUserMutation;

I keep getting the error:

Variable '$input_0' expected value of type 'SignupUserInput!' but got: {"email":"fdadsffd@fasdf.at","password":"@fdsad","clientMutationId":"1"}. Reason: Unknown field 'email' is not defined in the input type 'SignupUserInput'. (line 1, column 29):↵mutation SignupUserMutation($input_0:SignupUserInput!) {

What am I doing wrong here?