How to use the @turf/invariant.featureOf function in @turf/invariant

flattenEach(geoJson, feature => {
            featureOf(feature, 'LineString', 'Graph::fromGeoJson');
            // When a LineString if formed by many segments, split them
            coordReduce(feature, (prev, cur) => {
                if (prev) {
                    const start = graph.getNode(prev),
                        end = graph.getNode(cur);

                    graph.addEdge(start, end);
                }
                return cur;
            });
        });

flattenEach(geoJson, function (feature) {
        featureOf(feature, 'LineString', 'Graph::fromGeoJson');
        // When a LineString if formed by many segments, split them
        coordReduce(feature, function (prev, cur) {
            if (prev) {
                var start = graph.getNode(prev),
                    end = graph.getNode(cur);

                graph.addEdge(start, end);
            }
            return cur;
        });
    });

function pointToLineDistance(pt: Coord, line: Feature | LineString, options: {
    units?: Units,
    method?: "geodesic" | "planar",
} = {}): number {
    // Optional parameters
    if (!options.method) { options.method = "geodesic"; }
    if (!options.units) { options.units = "kilometers"; }

    // validation
    if (!pt) { throw new Error("pt is required"); }
    if (Array.isArray(pt)) { pt = point(pt);
    } else if (pt.type === "Point") { pt = feature(pt);
    } else { featureOf(pt, "Point", "point"); }

    if (!line) { throw new Error("line is required"); }
    if (Array.isArray(line)) { line = lineString(line);
    } else if (line.type === "LineString") { line = feature(line);
    } else { featureOf(line, "LineString", "line"); }

    let distance = Infinity;
    const p = pt.geometry.coordinates;
    segmentEach(line, (segment) => {
        const a = segment!.geometry.coordinates[0];
        const b = segment!.geometry.coordinates[1];
        const d = distanceToSegment(p, a, b, options);
        if (d < distance) { distance = d; }
    });
    return convertLength(distance, "degrees", options.units);
}

method?: "geodesic" | "planar",
} = {}): number {
    // Optional parameters
    if (!options.method) { options.method = "geodesic"; }
    if (!options.units) { options.units = "kilometers"; }

    // validation
    if (!pt) { throw new Error("pt is required"); }
    if (Array.isArray(pt)) { pt = point(pt);
    } else if (pt.type === "Point") { pt = feature(pt);
    } else { featureOf(pt, "Point", "point"); }

    if (!line) { throw new Error("line is required"); }
    if (Array.isArray(line)) { line = lineString(line);
    } else if (line.type === "LineString") { line = feature(line);
    } else { featureOf(line, "LineString", "line"); }

    let distance = Infinity;
    const p = pt.geometry.coordinates;
    segmentEach(line, (segment) => {
        const a = segment!.geometry.coordinates[0];
        const b = segment!.geometry.coordinates[1];
        const d = distanceToSegment(p, a, b, options);
        if (d < distance) { distance = d; }
    });
    return convertLength(distance, "degrees", options.units);
}