pub unsafe extern "C" fn lgraph_api_transaction_get_vertex_index_iterator_by_value_string(
txn: *mut lgraph_api_transaction_t,
label: *const c_char,
field: *const c_char,
key_start: *const c_char,
key_end: *const c_char,
errptr: *mut *mut c_char,
) -> *mut lgraph_api_vertex_index_iterator_t