input: Write a python function to find the minimum value in a list of numbers.
  assert find_minimum_value([10, 20, 30, 5, 99]) == 5
  assert find_minimum_value([100, 50, 200, 25, 75]) == 25
  assert find_minimum_value([-5, 0, 5, -10, 15]) == -10
output: def find_minimum_value(numbers):
      if not numbers:
          return None
      min_value = numbers[0]
      for num in numbers[1:]:
          if num < min_value:
              min_value = num
      return min_value