interface IBookStyle {
    initialLeftPageTransforms?: (width: number) => NamedTransform[];
}

interface NamedTransform {
    [name: string]: Transform3D;
}

interface Transform3D {
    cachedCss: string;
}

var style: IBookStyle = {
    initialLeftPageTransforms: (width: number) => {
        return [
            { 'ry': null }
        ];
    }
}
//!!!Type '{ initialLeftPageTransforms: (width: number) => { 'ry': any; }[]; }' is not assignable to type 'IBookStyle':
//!!!Types of property 'initialLeftPageTransforms' of types '{ initialLeftPageTransforms: (width: number) => { 'ry': any; }[]; }' and 'IBookStyle' are incompatible:
//!!!Call signatures of types '(width: number) => { 'ry': any; }[]' and '(width: number) => NamedTransform[]' are incompatible:
//!!!Types of property 'pop' of types '{ 'ry': any; }[]' and 'NamedTransform[]' are incompatible:
//!!!Call signatures of types '() => { 'ry': any; }' and '() => NamedTransform' are incompatible:
//!!!Index signatures of types '{ 'ry': any; }' and 'NamedTransform' are incompatible.