input: Write a function to sum the values of all dictionaries in a list.
  assert sum_dictionaries([{'a': 1, 'b': 2}, {'c': 3, 'd': 4}]) == 10
  assert sum_dictionaries([{'x': 5}, {'y': 10, 'z': 15}]) == 30
  assert sum_dictionaries([{'key1': 100}, {'key2': 200, 'key3': 300}]) == 600
output: def sum_dictionaries(dict_list):
      total_sum = 0
      for d in dict_list:
          total_sum += sum(d.values())
      return total_sum