function edge(style, samplerNum) {
    const mult = style === "dark" ? -1 : style === "light" ? 1 : style;
    return new EdgeExpr(expr_1.wrapInValue(mult), samplerNum);
}
returns an expression highlights edges where they appear
@param style `"dark"` for dark edges and `"light"` for light edges, or a
custom number or expression (between -1 and 1) for a more gray style of edge
@param samplerNum where to sample from