Function create_string_map_array 

pub fn create_string_map_array<T>(
    size: usize,
    null_density: f32,
    max_map_size: usize,
    key_len: usize,
) -> MapArray
where
    T: ArrowPrimitiveType,
    StandardUniform: Distribution<T::Native>,

Create a Map array with string keys and primitive values

Arguments:

• size: number of map entries in the array
• null_density: density of nulls in the map array (row-level nulls)
• max_map_size: maximum number of key-value pairs per map entry (actual size is random between 0 and max_map_size)
• key_len: length of each random string key