pub unsafe extern "C" fn manifold_set_properties(
mem: *mut c_void,
m: *mut ManifoldManifold,
num_prop: c_int,
fun: Option<unsafe extern "C" fn(new_prop: *mut f64, position: ManifoldVec3, old_prop: *const f64, ctx: *mut c_void)>,
ctx: *mut c_void,
) -> *mut ManifoldManifold