Function tsk_convert_newick 

pub unsafe extern "C" fn tsk_convert_newick(
    tree: *const tsk_tree_t,
    root: tsk_id_t,
    precision: c_uint,
    options: tsk_flags_t,
    buffer_size: usize,
    buffer: *mut c_char,
) -> c_int

Available on crate feature bindings only.