input: Write a python function to sort a list of strings by the number of vowels in each string in descending order.
  assert sort_list_by_vowels(["apple", "banana", "kiwi", "strawberry"]) == ["banana", "strawberry", "apple", "kiwi"]
  assert sort_list_by_vowels(["orange", "grape", "melon", "berry"]) == ["orange", "melon", "grape", "berry"]
  assert sort_list_by_vowels(["a", "e", "i", "o", "u"]) == ["a", "e", "i", "o", "u"]
  assert sort_list_by_vowels(["xyz", "pqr", "lmn", "stv"]) == ["xyz", "pqr", "lmn", "stv"]
output: def sort_list_by_vowels(strings):
      def count_vowels(s):
          return sum(1 for char in s if char in 'aeiouAEIOU')
      return sorted(strings, key=count_vowels, reverse=True)