Unable to Implement angular-schema-form-signature

Question

I'm unsure as to why an input field shows on the form when implementing this code.(ref: https://github.com/JamesGuthrie/angular-schema-form-signature)

This is my Schema:

{ "type": "object", "properties": { "signature": { "type": "string" } } }

This is my Form:

[
"name",
{
    "type": "tabs",
    "tabs": [
        {
            "title": "Tab1",
            "tabType": "top",
            "items": [
                {
                    "title": "Signature",
                    "key": "signature",
                    "type": "signature",
                    "width": 500,
                    "height": 100,
                    "resetButtonText": "Clear signature"
                }
            ]
        }
    ]
}
]