input: Write a python function to separate positive and negative numbers from a given list.
  assert separate_numbers([1, -2, 3, -4, 5, -6]) == ([1, 3, 5], [-2, -4, -6])
  assert separate_numbers([-1, -2, -3, -4]) == ([], [-1, -2, -3, -4])
  assert separate_numbers([10, 20, 30, -40, -50]) == ([10, 20, 30], [-40, -50])
output: def separate_numbers(numbers):
      positive_numbers = [num for num in numbers if num > 0]
      negative_numbers = [num for num in numbers if num < 0]
      return (positive_numbers, negative_numbers)