Function parse_with_functions 

pub fn parse_with_functions<'a, C: Tags + 'a, S: BuildHasher + Sync + Send + Default + 'a>(
    expression: &str,
    functions: HashMap<String, Function<'a, C>, S>,
) -> ParseResult<'a, C>

Errors

Parse MapLibre Expression (incomplete implementation) and return function that evaluates the expression with the provided context