Function buffer_linestring 

pub fn buffer_linestring(
    line: &LineString,
    distance: f64,
    options: &BufferOptions,
) -> Result<Polygon>

Generates a buffer around a linestring

Creates a polygon buffer around a linestring using parallel offset curves on both sides, with configurable cap and join styles.

Arguments

• line - The linestring to buffer
• distance - Buffer distance (positive for expansion, negative for contraction)
• options - Buffer options

Errors

Returns error if linestring is invalid or has insufficient points