First attempt at creating a typescript interface for the GeoServer "grass" SLD. Notice "Grass" is in the definition!

grass.sld.d.ts

interface IGrassTestStyledLayerDescriptor {
    version: string;
    namedLayers: {
        Grass: {
            userStyles: Array<{
                defaultsPerSymbolizer: boolean;
                rules: Array<{
                    symbolizer: {
                        Polygon: {
                            fill: boolean;
                            stroke: boolean;
                            strokeColor: string;
                            strokeWidth: string;
                        };
                    };
                    id: string;
                    name: string;
                    description: string;
                }>;
                name: string;
                title: string;
                description: string;
                propertyStyles: any;
                defaultStyle: {
                    fillColor: string;
                    fillOpacity: number;
                    strokeColor: string;
                    strokeOpacity: number;
                    strokeWidth: number;
                    strokeDashstyle: string;
                    pointRadius: number;
                    graphicName: string;
                };
                id: string;
                layerName: string;
            }>;
            namedStyles: Array<any>;
            name: string;
        };
    };
}