Function sexpy::context

pub fn context<I, E, F, O>(context: &'static str, f: F) -> impl Fn(I) where
    E: ParseError<I>,
    F: Fn(I) -> Result<(I, O), Err<E>>,
    I: Clone, 

create a new error from an input position, a static string and an existing error. This is used mainly in the context combinator, to add user friendly information to errors when backtracking through a parse tree