Write by_length(words) returning words sorted by length (shortest first); equal lengths keep their original order.
by_length(['pandas', 'sql', 'numpy', 'r']) → ['r', 'sql', 'numpy', 'pandas']
by_length([]) → []
Submit runs 3 tests, including hidden edge cases.
Each hint gives a little more help. Try on your own first.
Run your code to see the output here.