Function runnable_lambda 

pub fn runnable_lambda<F, I, O>(func: F) -> RunnableLambda<F, I, O>
where
    F: Fn(I) -> Result<O> + Send + Sync,
    I: Send + Sync + Clone + Debug + 'static,
    O: Send + Sync + Clone + Debug + 'static,

Create a RunnableLambda from a function.