input: Write a python function to return the list of first n natural numbers.
  assert generate_numbers(5) == [0, 1, 2, 3, 4]
  assert generate_numbers(10) == [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
  assert generate_numbers(0) == []
  assert generate_numbers(3) == [0, 1, 2]
output: def generate_numbers(n):
      return list(range(n))