input: Write a Python function that accepts a list of integers and returns the sum of their absolute values, multiplied by the product of their signs. If the list is empty, the function should return None.
  assert calculate_sum_and_sign([1, 2, 2, -4]) == -9
  assert calculate_sum_and_sign([0, 1]) == 0
  assert calculate_sum_and_sign([1, 1, 1, 2, 3, -1, 1]) == -10
  assert calculate_sum_and_sign([]) == None
  assert calculate_sum_and_sign([2, 4,1, 2, -1, -1, 9]) == 20
  assert calculate_sum_and_sign([-1, 1, -1, 1]) == 4
  assert calculate_sum_and_sign([-1, 1, 1, 1]) == -4
  assert calculate_sum_and_sign([-1, 1, 1, 0]) == 0
output: def calculate_sum_and_sign(lst):
      if not lst:
          return None
      total_abs_sum = sum(abs(x) for x in lst)
      sign_product = 1
      for num in lst:
          if num < 0:
              sign_product *= -1
      return total_abs_sum * sign_product