pub unsafe extern "C" fn igraph_tree_from_parent_vector(
graph: *mut igraph_t,
parents: *const igraph_vector_int_t,
mode: igraph_tree_mode_t,
) -> igraph_error_tpub unsafe extern "C" fn igraph_tree_from_parent_vector(
graph: *mut igraph_t,
parents: *const igraph_vector_int_t,
mode: igraph_tree_mode_t,
) -> igraph_error_t