Function parse 

pub fn parse<T, F>(
    file: &str,
    source: &str,
    format: &MapFormat<'_>,
    terrain: impl Fn(&str) -> Option<T>,
) -> Result<GridMap<T, F>, Vec<ContentError>>
where
    T: Copy + Default,
    F: MapFeature,

Parses map source (errors attributed to file), resolving legend terrain ids with terrain. Reports every problem with its line and column.