Convert Boolean to condition in Expression tree

Hi Experts How I Can convert this statement to Expression tree:

x=>x.Contains("bla")

thanks

var parameter = Expression.Parameter(typeof(string), "x");
var lambda = Expression.Lambda<Func<string, bool>>(
    Expression.Call(
        parameter,
        "Contains",
        Type.EmptyTypes,
        Expression.Constant(
            "blah"
        )
    ),
    parameter
);